I enjoyed this book, although as I went on I found the author's light and folksy style starting to wear a bit thin at times. The book is very easy to read but the author has either picked up, or deliberately adopted, a middle-America tone to his writing since arriving in the States from Afghanistan. We get phrases like "he was just that kind of guy" and "...but wait, as they say on late night TV commercials, that's not all...". There is also regular use of dialogue which for the most part clearly cannot come from direct reporting. It all serves to make the book feel friendly and approachable, but possibly at the expense of intellectual rigour. Still, it is a perfectly enjoyable read (for the most part).
I'm nowhere near even thinly read on this subject, in fact I last gave the Crusades serious attention nearly thirty years ago in the sixth form (and then obviously from an exclusively western perspective), I've heard a couple of In Our Time's on Islamic subjects and my understanding of contemporary issues in the middle east is about the same as any other Radio 4 listening broadsheet reader. So, given that, I'm in no position to judge the accuracy of the author's history but on issues where politics often clouds fair and accurate historical judgement (eg, the Crusades, Suez, Israel/Palestine, and the world post-9/11) the book is scrupulously balanced and fair minded.
In any book that covers such a vast topic and period there is inevitable glossing over and simplification but, given the limitations of any "big picture" history book for non-academic readers, I recommend this and an interesting and worthwhile read.