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.

Nasr's basic thesis is that the deteriorating condition of nature is an indication of man's waning spirituality. Unfortunately, the book works more as a 'history of philosophy and science' without discussion on his thesis.