I liked The Bottom Billion, but was disappointed with this - bits of it were fairly patchy, or used some proxies that don't really show what he argued they showed. I'm not a stats expert, so I won't go into detail, but I know a number of academics that really hate this book because they argue that the statistics are deeply misleading.
What I will comment on, is his manipulation of the case studies to prove his point. In particular, in his case study of Cote d'Ivoire, he talked about Robert Guei leading a coup against Laurent Gbagbo in 2002, which simply isn't true. I was in Cote d'Ivoire at the time of the events in question, and it was universally known that Guei had nothing to do with the coup, which was run by a group of Northern officers and politicians. When it became clear that the coup wouldn't succeed in Abidjan, Gbagbo took the opportunity to wipe out some political opponents, including Guei and Alassane Ouattara, who narrowly escaped over the wall to the German Ambassador's house. Of course, if you accept the government line, you would believe that Guei was storming the radio station in his pyjamas, surrounded by his wife, kids and domestic staff, all of whom were killed in the firefight.
A basic google search could have turned up this information (I've just done one), but instead he chose to use a misleading case study that 'proved' his point. It just so happens that I know enough about Cote d'Ivoire to know that this was wrong, but it makes me wonder about everything else in the book that I don't know a lot about.