As soon as they became recognizably human, men and women - in their hunger to understand their own presence on earth and the mysteries within and around them - began to worship gods. Karen Armstrong's masterly and illuminating book explores the ways in which the idea and experience of God evolved among the monotheists - Jews, Christians and Muslims.

Weaving a multicolored fabric of historical, philosophical, intellectual and social developments and insights, Armstrong shows how, at various times through the centuries, each of the monotheistic religions has held a subtly different concept of God. At the same time she draws our attention to the basic and profound similarities among them, making it clear that in all of them God has been and is experienced intensely, passionately and often - especially in the West - traumatically.

Some monotheists have seen darkness, desolation and terror, where others have seen light and transfiguration; the reasons for these inherent differences are examined, and the people behind them are brought to life.

We look first at the gradual move away from the pagan gods to the full-fledged monotheism of the Jews during the exile in Babylon. Next considered is the development of parallel, yet different, perceptions and beliefs among Christians and Muslims.

The book then moves "generationally" through time to examine the God of the philosophers and mystics in all three traditions, the God of the Reformation, the God of the Enlightenment and finally the nineteenth- and twentieth-century challenges of skeptics and atheists, as well as the fiercely reductive faith of the fundamentalists of our own day.

Armstrong suggests that any particular idea of God must - if it is to survive - work for the people who develop it, and that ideas of God change when they cease to be effective. She argues that the concept of a personal God who behaves like a larger version of ourselves was suited to mankind at a certain stage but no longer works for an increasing number of people.

Understanding the ever-changing ideas of God in the past and their relevance and usefulness in their time, she says, is a way to begin the search for a new concept for the twenty-first century. Her book shows that such a development is virtually inevitable, in spite of the despair of our increasingly "Godless" world, because it is a natural aspect of our humanity to seek a symbol for the ineffable reality that is universally perceived.