Paul Williams has written a short but very ambitious book, designed to cover causes of war and crisis in Africa as well as responses to them. He succeeds, in the sense that anyone coming to the subject for the first time will find a capable exposition of the main issues, with substantial citations from other scholars and a thorough bibliography. Sometimes, though - as in the chapter on the African Union - the result is a bit of a cut-and-paste job, which doesn't add much if anything to what is already available. The thematic chapters are rather uneven. The weakest is on ethnicity, which spends most of its length talking about Rwanda (an apparent obsession of the author) although, as he admits, Rwanda was a socio-economic conflict, not an ethnic one.
On the other hand, the book is based almost entirely on non-African sources (though the occasional African scholar gets to put a word in) and all of the sources are in English, so leaving out a substantial French literature and a modest Portuguese one. The book is also firmly in the American political science tradition, and seems aimed primarily at American students. There's little sense in the text of first-hand engagement with the continent, and the introduction is rather coy about how much, if any, actual time the author spent doing research there, as opposed to speaking to other western scholars. Perhaps inevitably for an American, there's also very little sense of the importance of the independence wars, and their consequences for conflict in Africa subsequently. It's also quite heavy on models and statistical correlations.
If you are new to the subject and wondering where to start, this book can provide some pointers, otherwise, William Reno's new book on the same subject (which I reviewed a few months ago) is much better.