The holy rage of people who live by the letter of the Word

It is widely remarked that we now live in a fundamentalist world. Max Weber, the early 20th-century sociologist who argued that modernity and secularism were inextricably linked, sadly could not have been more wrong.

Whether you are in Beirut, Brooklyn or Barnet, two of the most discussed films of the past year have been Mel Gibson's The Passion of the Christ and Michael Moore's Fahrenheit 9/11 , and they agree that our age is marked by extreme political religion. These two books offer answers as to how this has happened.

God's Last Words is a broad, anecdotal history of the role of the Bible in Western culture. David Katz argues for the Bible's "significance in manufacturing the common code of the English-speaking world" and traces its cultural and political centrality across 500 years of European and American history. Both the Reformation and the Enlightenment began as arguments over scriptural interpretation; during the English Civil War, the American Civil War and the Spanish-American War, soldiers carried specially printed pocket-size Bibles; in the past century, increasing numbers of Americans embraced the literalist scriptural interpretations of popular preachers such as Jerry Falwell and Pat Robertson. Now, "more than 20 per cent of the American population - 50 million Americans - can be called 'Evangelical Protestants'", who, like Martin Luther and the 16th-century Protestant reformers, fetishise the very words of the Bible as the centre of faith.

Katz reminds us how influential the bestselling book of all time has been.

European reformers in the 16th century insisted that the text of the Bible alone provided a template for devotional and political life. Two centuries later, the Enlightenment reinterpreted the words of Scripture and religion more broadly towards a metaphorical and increasingly godless morality. In the fading years of the 20th century, in the most powerful country in a world again torn apart by holy wars, a popular movement with increasing political power has returned to a scriptural literalism that occasionally resembles a traditionally Protestant approach to the Bible.

Reading the Bible has been, and continues to be, an activity of considerable political impact; the rise of fundamentalism in the US stands as implicit proof of Katz's argument. But Katz is unwilling to engage in the activity whose history he claims to narrate. While the subtitle, "Reading the English Bible from the Reformation to Fundamentalism", boldly sets out the subject, each of its four main terms is largely absent from the book itself. "Reading" means both the literal act of encountering page-bound words and subjective interpretation. In the book, however, Katz dismisses the possibility of active interpretation. In discussing the causes of the English Civil War, he notes: "As Hobbes correctly observed, there was a certain element in the biblical narrative that worked against political authority." This is to say that Scripture itself encourages anti-authoritarian sentiment - news to both the court of Henry VIII and the White House of George W. Bush, where scriptural reference has been a foundation of political authority.

The Bible is also oddly absent. While Katz lists multiple different translations and editions, he makes no reference to their contents. The third of Katz's subject areas, the Reformation, which was undoubtedly an important event in the history of scriptural interpretation, takes place between chapters. Finally, American fundamentalism is passed over in the closing three pages of the book, half of which is devoted to the Scofield Reference Bible of 1909 - the biblical text used by American fundamentalists and, according to Katz, "the single most important publication in the history of messianic theology". He does not quote it or discuss its contents.

God's Last Words is a shopping list of men who argued over or wrote about the Bible, and a flurry of historical anecdotage. We have no sense of how, or why, texts are interpreted. For a consideration of fundamentalism as a style of thinking - a world-view rather than a movement - we must turn to Malise Ruthven.

Ruthven is a scholar known for his work on Islam, but he has also written on popular religion in America. In Fundamentalism, he reflects on both areas with an urgency animated by the events of the past three years.

"Until the mid-1970s," he writes, "it was widely assumed that politics was breaking away from religion and that as societies became more industrialised, religious belief and practice would be restricted to private thoughts and activities." The assumption was wrong. In this short, eloquent book, Ruthven traces the hallmarks of the new and terrifyingly powerful movements united under what he calls "the F-word".

The book is divided loosely into three sections. The first treats Christian fundamentalism in America. The word itself appeared early in the 20th century in southern California with a pamphlet series called "The Fundamentals: A Testimony of Truth". Funded by two devout Christian brothers who had made a fortune in the oil business, the pamphlets set out a series of basic beliefs: the inerrancy of Scripture; the direct creation of the world by God; the authenticity of miracles; and the imminent return of Christ to the world.

These beliefs are shared by the three religions founded in the US: Mormonism, Seventh Day Adventism and the Jehovah's Witnesses. Ruthven suggests reasons why these fundamentalist religions should have taken hold in the US rather than other equally developed nations. The separation of church and state enshrined in the American Constitution has provided, paradoxically, a fertile ground for the haphazard and populist growth of religious extremism. As Ruthven wrote in in his earlier book on American popular religion, The Divine Supermarket: "Freedom of worship means freedom, not just from the coercive power of the state, but from public scrutiny - freedom from anything resembling religious quality control."

While Protestant fundamentalism is an American phenomenon, fundamentalism itself is today global, and Ruthven moves on to note a series of family resemblances between fundamentalist movements across the globe: they are monocultural, nostalgic for a lost past and, to varying degrees, misogynist. In each case, the tendency arises in reaction to a perceived threat. The current rash of fundamentalisms is a reaction against the globalising spread of modern Western habits of thought and modes of being.

As Ruthven writes: "Where pork is not available, no one has to make a decision about whether to eat hot-dogs." Fundamentalism is not a monolithic movement but a style of thinking and a way of approaching the world.

In the third section, Ruthven gives examples from Catholic Northern Ireland, Sri Lanka and both Hindu and Sikh groups in India, to argue that nationalism and fundamentalism share intellectual and psychological tendencies. Nationalism is, of course, a form of proxy religion; the clearest examples of Ruthven's argument are Israel and America, where celebration of the state shades often into religious polemic. In the final pages of the book, Ruthven expresses his hopes that the pluralism that defines modern societies and is enabled by modern technology will lead people away from the extremes of religious violence.

Fundamentalism, he writes, "is religion materialised, the word made flesh, as it were, with the flesh rendered, all too often, into shattered body parts by the forces of holy rage". The implicit metaphor behind this powerful image is, of course, an Islamic suicide bomber. Both of these books warn us that fundamentalism is not, however, restricted to societies and wars on the far side of the world; it is also one strand of the cultural DNA of the modern West.

Daniel Swift is completing a PhD at Columbia University, New York, US.