There was an entry on Lines from a Floating Life in June 2005 when I first got Nasr’s The Heart of Islam, which I am now reading carefully as I think what to say here on the subject soon. At the end of that entry I may have been a bit harsh. Certainly one great plus in the book is to enable the rest of us to appreciate the diversity and complexity of Islamic ideas and practices, and to grasp the import of the fact that Islam has no central authority like, say, the Vatican.
I have also just reread The Koran: A Very Short Introduction by Michael Cook which deservedly is in this Guardian list, Robert Irwin’s top 10 books on Islam and Islamic culture. It really is fascinating.