I've been working through my backlog of unread history books this year. This one is a bit unusual in that I am not and never have been professionally engaged on the areas in question (actually not quite true - Hourani has a half page on the Western Sahara, but it is marred by inaccuracy). It's an interesting survey - I have been reading a bit about the origins of Islam (both Rogerson's books and this piece by Patricia Crone) but Hourani's book starts from there and takes the narrative up to the late 80s. (The 2002 afterword, by someone else, suffers from not saying enough about Iraq.)
What I most liked about the book was the emphasis on social and economic as well as political history - and that is a big admission for me, because normally I only like the political history bits. Hourani modestly claims that in this he is following the example of the great Ibn Khaldūn, but I'm sure he brings an extra six centuries of historiography to bear as well (I am sorry to say that I have read only extracts of Ibn Khaldūn; I see the Muqaddimah is on-line here though.) By concentrating on philosophy and culture he makes a good implicit case that currents of Islamic thought had a greater direct impact on local politics than perhaps the equivalents for Christianity.
Which links neatly to my only grounds of dissatisfaction with the book; which are (rather unreasonably of me, since he covers a pretty large chunk of the world) that it doesn't look widely enough. Iran and Persia are barely mentioned; likewise India, the Balkans and Cyprus, all of which are important interfaces between Islam and other faiths. Turkey proper, because of the longevity of the Ottoman Empire, gets a bit more coverage, as does Al-Andalus, but sub-Saharan Africa, Indonesia, Central Asia and Afghanistan are basically invisible. OK, the book is technically about Arabs rather than Muslims, but it concentrates so much on Islam (and correspondingly less on Arab Christians, except in Lebanon) that I felt the non-Arab Muslims got rather short shrift.
Anyway, well worth reading.