This book is one of the few books (along with calculus and other basic professional books) that I used in college and still use today.
The three main three religions; Judaism, Christianity and Islam, along with other philosophical and religious traditions are explained in a clear unbiased way. I, specifically, learned a lot about Taoism, Hinduism and Buddhism. Books of this sort help people understand each others' customs and motives and make tolerance an achievable task instead of an impossible one.