History lessons in early Islam

Having just taught a course in which a look at early Islam was necessary, being led to this book review seemed very intriguing.History lessons | Comment is free: it's a real potential humdinger as the reading of the history undermines the Jihadist/Islamist line on Khalifah: here's a quote from the review to give you the flavour. "Fatah believes, there is only one conclusion to be drawn: the historical Islamic states were not organised around Islam, but ethnicity (Arab over non-Arab), power, and expansion (both through conflict and conversion). In other words, non-theocratic, non-theological, rather secular concerns: hardly what Islamists have us believe. Thus, Fatah concludes, the Islamist idea of an Islamic state is just a mirage. It is neither corroborated in the original sources of Islam - the Qur'an and the prophet's practice - nor in the actual practice of the first generations of Islam."
I'm considering buying the book. That said, the comments on the article quickly reveal the difficulties the thesis might face, and some suggest that it still may not make a great difference if accepted.
Chasing a Mirage: The Tragic Illusion of an Islamic State