Yet over 100m copies of the Bible are sold or given away every year. Annual Bible sales in America are worth between $425m and $650m; Gideon's International gives away a Bible every second. The Bible is available all or in part in 2,426 languages, covering 95% of the world's population.

The Koran is not only the most widely read book in the Islamic world but also the most widely recited ("Koran" means "recitation"). There is no higher goal in Muslim life than to become a human repository of the Holy Book; there is no more common sound in the Muslim world than the sound of Koranic recitation.

Reciting the Koran is the backbone of Muslim education. One of the most prized honorifics in Islamic society is "hafiz" or "one who has the entire scripture off by heart". Do so in Iran and you get an automatic university degree. The great recitors compete in tournaments that can attract audiences in the hundreds of thousands-the world cups of the Islamic world. The winners'CDs become instant bestsellers.

The Bible and the Koran have both gone global. In 1900, 80% of the world's Christians lived in Europe and the United States. Today 60% live in the developing world. More Presbyterians go to church in Ghana than in Scotland. In 1900 Islam was concentrated in the Arab world and South-East Asia. Today, there may be as many practising Muslims in England as there are practising Anglicans; though in the 20th century, at least, Islam's expansion has mostly come about through population growth and migration, rather than conversion. Muslim "missionary" activity is aimed more at reinvigorating the faithful, and encouraging them to greater zealotry, than at winning new souls.

This mountain of Holy Books is a giant refutation of the secularisation thesis-the idea that religion recedes as the world modernises. "The book lives on among its people," Constance Padwick, a scholar of the Koran, has written. "For them these are not mere letters or mere words. They are the twigs of the burning bush, aflame with God." The same can be said of the Bible.

It also poses a couple of intriguing questions. Why are today's Christians and Muslims proving so successful at getting the Word out? And who is winning the battle of the books? Is either of the world's two great missionary religions gaining an edge when it comes to getting their Holy Books into people's hands and hearts?

The straightforward answer to the first question is that Christians and Muslims are both proving remarkably adept at using the tools of modernity-globalisation, technology and growing wealth-to aid the distribution of their Holy Books. "Give me Scotland or I die," John Knox once cried. Today's faithful aim for the world.

The combination of globalisation and rising wealth is proving to be a bonanza for both religions. The most prolific producer of Christian missionaries, on a per head basis, is now South Korea. The biggest Bible publishing houses are in Brazil and South Korea. An interlinked global network of 140 national or regional Bible Societies pools resources to reach its collective goal of putting a Bible in the hands of every man, woman and child on the planet. The American Bible Society, the biggest of the lot, has published more than 50m Bibles in atheist China.

Saudi oil wealth is supercharging the distribution of the Koran. The kingdom gives away some 30m Korans a year, under the auspices of either the Muslim World League or individual billionaires, distributing them through a vast network of mosques, Islamic societies and even embassies. Go to FreeKoran.com and you can have a free book in your hands in weeks.

Saudi-funded dissemination of the Koran, along with literature promoting the stern Saudi understanding of Islam, may not have much direct effect on Christians, or the unchurched. But it does increase the relative weight, within Islam, of teachings which tend to sharpen the Christian-Muslim divide. For example, traditional Muslim teaching stresses those passages in the Koran which affirm the Christian Gospel and the Hebrew Torah as valid revelations of God and paths to salvation. But there is a harsher, Saudi-influenced view which insists that since Muhammad delivered the final revelation, Christianity and Judaism have lost their power to save.

The Muslim diaspora and Muslim missionaries are bringing the faith to previously untouched areas. The Tablighi Jamaat ("the group that propagates the faith") is a global network of part-time preachers who dress like the Prophet, in a white robe and leather sandals, and travel in small groups to spread the Word. Their annual gatherings in India and Pakistan attract hundreds of thousands.

Technology is proving to be a friend of the Holy Books. You can consult them on the internet. You can read them on your "Psalm pilot" or mobile phone. You can listen to them on MP3 players or iPods ("podcasting" has given rise to "Godcasting"). Want to "plug into God without unplugging from life"? Then simply buy a Go Bible MP3 player. Want to memorise the Koran? Then buy an MP3 player that displays the words as you listen. Want to network with like-minded people? Then the eBible allows you to discuss biblical passages with virtual friends.

Several television channels and radio stations do nothing but broadcast the Koran. At the other end of the technological spectrum, the American Bible Society produces an audio device, powered by a battery or hand crank and no bigger than a couple of cigar boxes, that can broadcast the Bible to a crowd of a hundred. Getty Images Getty Images

A well-thumbed Book

There is a difference, however, between getting and understanding a Holy Book. Here both Christianity and Islam suffer from serious problems. Americans buy more than 20m new Bibles every year to add to the four that the average American has at home. Yet the state of American biblical knowledge is abysmal. A Gallup survey found that less than half of Americans can name the first book of the Bible (Genesis), only a third know who delivered the Sermon on the Mount (Billy Graham is a popular answer) and a quarter do not know what is celebrated at Easter (the resurrection, the foundational event of Christianity). Sixty per cent cannot name half the ten commandments; 12% think Noah was married to Joan of Arc. George Gallup, a leading Evangelical as well as a premier pollster, describes America as "a nation of biblical illiterates".

Muslims greatly prefer to read the Koran in the original Arabic. Yet the archaic language and high-flown verse, while inspiring, can also be difficult to understand even for educated Arabic speakers. And only 20% of Muslims speak Arabic as their first language. Illiteracy rates are high across the Muslim world. Many students of the Holy Book do not understand much of what they are memorising.

This needs to be kept in mind when considering who is winning the battle of the books. For some, the question is an abomination. Can't both sides win by converting the heathen? And aren't Christianity and Islam fellow Abrahamic faiths-different versions of the Truth? Others worry that the question is impossible to answer, since there are no systematic figures on the distribution of the Koran, and the battle's front-line cuts through some of the darkest and most dangerous places on the planet. Muslims would argue that their struggle was aimed more at galvanising their own flock than at converting unbelievers. But Islam's relative introversion doesn't make for peaceful coexistence. In many parts of the world, Islamic authorities have reacted furiously to attempts by Christians to entice Muslims to "apostasise" or renounce their faith; in traditional Islamic law, the penalty for apostasy is death; and encouraging believers to apostasise is also treated as a crime.

In many parts of the world, battle seems to be in progress. The Saudis will not allow the Bible to be distributed on their soil. Many Evangelical Christians are fixated on what they call the 10/40 window-the vast swathe of the Islamic world in Africa and Asia that lies between latitudes 10 and 40 north of the equator. The Southwestern Baptist Theological Seminary in Texas has even created a masters degree to train missionaries in the art of converting Muslims. Some Evangelicals produce counterfeit Korans that are designed to plant doubt in Muslim minds.

And the battle of the books is certainly at the heart of the battle between the two religions. People who get hold of Bibles or Korans may not read them or understand them. Unless they are introduced to the books they will certainly remain heathens. Even an imperfect report on the state of the battle tells us a lot about the world's two great missionary religions.

The Christians entered the 21st century with a big head start. There are 2 billion of them in the world compared with 1.5 billion Muslims. But Islam had a better 20th century than Christianity. The world's Muslim population grew from 200m in 1900 to its current levels. Christianity has shrivelled in Christendom's European heart. Islam is resurgent across the Arab world. Many Christian scholars predict that Islam will overtake Christianity as the world's largest religion by 2050.

More recently, though, Muslims complain that the "war on terror" is making it much more difficult to spread the Koran. Contributions to Muslim charities have fallen since September 11th 2001. Several charities have had their funding disrupted. Missionary organisations such as the Tablighi Jamaat are under investigation by Western intelligence services, on the grounds that they may be way-stations to jihadism. And Muslims confront much bigger long-term problems in the battle of the books.

The first is Christianity's superior marketing skills. Its religious publishing houses are big businesses. Thomas Nelson, which was once owned by a former door-to-door Bible salesman, was bought in 2005 for $473m. And secular publishing houses have also got religion: HarperCollins bought Zondervan, a religious book publisher, in the late 1980s, and now most mainstream publishers are trying to produce their own Bibles. As a result, all the tricks of the publisher's trade are being applied to the Bible.

Consider product proliferation. Thomas Nelson publishes 60 different editions of the Bible every year. The Good Book now comes in all colours, including those of your college. There are Bibles for every sort of person, from "seekers" to cowboys, from brides to barmen. There is a waterproof outdoor Bible and a camouflage Bible for use in war zones. The "100 minute Bible" summarises the Good Book for the time-starved.

Consider user-friendliness. There are prayer books in everyday vernacular or even street slang ("And even though I walk through/The Hood of death/I don't back down/for you have my back"). Or consider innovation. In 2003 Thomas Nelson dreamt up the idea of Bible-zines-crosses between Bibles and teenage magazines. The pioneer was Revolve, which intercuts the New Testament with beauty tips and relationship advice ("are you dating a Godly guy?"). This was quickly followed by Refuel, for boys, and Blossom and Explore, for tweens.

The world's richest and most powerful country contains some 80m Evangelicals

There are toddler-friendly versions of the most famous Bible stories. The "Boy's Bible" promises "gross and gory Bible stuff". The "Picture Bible" looks like a super-hero comic. "God's Little Princess Devotional Bible" is pink and sparkly.

There are about 900 English translations of the Bible, ranging from the grandiloquent to the colloquial. There are translations into languages, such as Inupiat and Gullah, that are spoken by only handfuls of people. Bob Hudson, of the American Bible Society, wants everybody on the planet to be able to claim that "God speaks my language". A couple of eccentric geeks have even translated the Bible into Klingon, a language spoken only by scrofulous space aliens on "Star Trek".

Publishers are producing sophisticated dramatisations of the Bible with famous actors and state-of-the-art sound effects. Zondervan's "The Bible Experience" features every black actor in Hollywood from Denzel Washington to Samuel L. Jackson. Other outfits are making films that dramatise Bible stories as faithfully as possible.

And then there are the spin-offs. A "fully posable" Jesus doll recites famous passages of the Good Book. There are Bible quiz books, stuffed with crosswords and other word puzzles, and Bible bingo games. There are Bible colouring books, sticker books and floor puzzles. There is even a Bible-based juke box that plays your favourite biblical passages.

Muslims have also gone into the Holy Book business, but nowhere near as enthusiastically as Christians. This is partly because their commercial publishing houses are smaller and less sophisticated, but also because Muslims believe that the Koran is the literal word of God-dictated to Muhammad (who was himself illiterate) by the Angel Gabriel and then written down by Muhammad's followers. "The Koran does not document what is other than itself," one scholar notes. "It is not about the truth. It is the truth."

This makes Muslims uncomfortable with translations. The Holy Book says sternly that "we have sent no messenger save with the tongue of his people." Today most Muslims tolerate translations-there are now more than 20 English translations-but do so reluctantly. Most translations are as literal as possible. Pious Muslims are expected to learn God's language.

The second advantage the Christians have is America. The world's richest and most powerful country contains some 80m Evangelicals. It supports more missionaries, more broadcasting organisations and more global publishers than any other country. Despite some countries' oil wealth, the Koran's heartland is relatively poor. The Arab world has one of the highest illiteracy rates in the world, with a fifth of men and two-fifths of women unable to read. It also has one of the lowest rates of internet usage.

The third big advantage is the West's belief in religious freedom-guaranteed in America by the constitution, and in Europe by an aversion to religious persecution caused by centuries of it. The heartland of Islam, by contrast, is theocratic. The Saudi Ministry of Islamic Affairs, Endowment, Call and Guidance employs 120,000 people, including 72,000 imams. Saudi Arabia bans non-Islamic worship and regards attempts to convert Muslims to another faith as a criminal offence. Pakistan has witnessed the attacks on Christian missionaries. Sudan punishes "religious deviation" with imprisonment.

Christian Evangelists complain that this creates an uneven playing field: Muslims can build giant mosques in "Christian lands" while Christians are barred from distributing Bibles in Saudi Arabia and Iran. But uneven playing fields tend to weaken the home players. Open competition is a boon to religion: American Evangelism has flourished precisely because America has no official church. And theocracy is ultimately a source of sloth and conservatism. "The Book and the Koran", by Muhammad Shahrur, which tried to reinterpret the Koran for modern readers, was widely banned in the Islamic world, despite its pious tone and huge popularity.

This state-of-the-battle report comes with a health warning. Predicting the fate of religions is unwise, for they can burn or gutter in unpredictable ways. But two things are certain in the battle of the books. The first is that the urge to spread the Word will spark some of the fiercest conflicts of the 21st century.

The area that is being most heavily fought over-sub-Saharan Africa-is a tinder box of failed states and ethnic animosities. The second is that the Bible and the Koran will continue to exercise a dramatic influence over human events, for both good and ill. The twigs of the burning bush are still aflame with the fire of God.

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