Light in the Shadow of Jihad is eloquent and seemingly heart-felt sermon, but a little short on substance, it seemed to me. Zacharius' main points are that relativism is unhelpful in meeting the needs of modern man, and unprincipled absolutism -- a la bin Laden -- is no good either. It's also kind of a patriotic crie de couer. All right. Rousing, but not that enlightening. But maybe that's because I've heard the sermon before.
I tend to agree with most of what Zacharius says. But from the title I thought I might learn something about Islam here. I did not. The book is primarily about relativism. Zacharius is from India, but he seems to know more about Western philosophy than about non-Western religions, which is a pity, because Americans do need to learn about other religions from a prophetic, rather than uncritically affirming or denying, perspective. If that is what you are looking for, I recommend Paul Fregosi (Jihad), Maxime Rodinson (Mohammed), Bernard Lewis, V.S. Naipaul, or Peter Partner (God of Battles) for an honest and more informed look at Islam. I also highly recommend the works of Vishal Mangalwadi, another Indian Christian who writes with passion, but also it seems to me broader knowledge of other religions. If you want an eloquent sermon on the errors of relativism, this book may meet your need, however.