To my knowledge this is one of the first (if not the first) attempt of its kind in the English language -- an attempt to present a clear and detailed view of the various dimensions of Islam from within (i.e. from the perspective of those who believe and live by it). The various contributors are experts in their respective areas and have treated their respective subject matter with the loving care that is the hallmark of those who write from the heart.

If you don't know much about Islam, this isn't the place to start. The authors and perspectives are overwhelmingly Sufi, and strain to present mystical Islam in Christian terms. They generally also represent modernist Islam, assimilated to Western ideas. So this isn't mainstream Islam. But if that's what you're interested in, this is a great book. Of course some essays are better than others, but overall it's a good read. I learned a lot.

Edit - here we are, about 6 years later, and I understand what this book is. Nasr is not a normal Muslim, nor are any of the contributors to this "study." They are "Traditionalists," followers of Rene Guenon. You can read about traditionalism in Sedgwick's "Against the Modern World." What this means is that this is a great book if you want to study "Traditionalist Spirituality," but not if you want to study Islam. Let me recommend Reza Aslan's "No God but God" if you haven't studied Islam much and are just curious. If you want a better introduction to Sufism, consider books by Henri Corbin (also a traditionalist, but more faithful to his declared subjects). There are lots of others of course.