This book is an excellent overview of the various forms of faith in the Christian world from North Africa to Persia, whether it be Catholic, Orthodox, or Protestant.
The one concern that I do have with this book, is that the author seems to feel that Christianity is a declining faith in the middle east, rather than growing. I have contact with Christians who minister in the middle east, and the picture that they paint is totally different. They say that persecution within the Muslim countries has opened doors for the Good News, and tens of thousands are responding.
Like all reference books, it is written with a slant towards their understanding. That being said, I haven't read anything else that is as thorough as this. I especially liked the inserts that deal with various points of interest. I recommend this book!