Highly accessible piece of work into the early history of Islam although I did have my doubts as to its accuracy and detail. Still, considering that it's such a complicated history and that as Hazleton acknowledged, she drew heavily from a 39-volume translation of al-Tabari's historical account of early Islam, it's not really a surprise that she couldn't really go into great depth within a mere 200-page book.
The book seems slightly biased towards Shia Islam and some online reviews have dismissed the book based on this point, but I guess Hazleton had to spin her narrative in a certain direction in order for it to hold readers. I wouldn't say it is a serious work of history but I find it highly engaging as an entry point into the subject; at certain points, I had to put the book down and wonder/despair at the missed opportunities.
All in all, highly recommended but do take it with a pinch of salt, and use it to spur you on to find out more about the topic.