I recently finished reading Graeber's Debt and highly recommend it. One caveat is that his discussion of slavery is difficult to maintain. He runs into difficulty on the level of slavery during the middle ages and his contention that no one "really" believed the, shifting to be sure, justifications for slavery. It's not clear to me how or if these errors forwards his argument but it is a serious error. He might want to at least consult one David Bryon Davis many books.
The book is also very much a polemical attempt at rethinking world history and should be read as such, which means checking the facts before repeating them. However, the argument is well worth the time. He writes with a sort of breezy pop-donishness that eases the process. I'll have more to say about this book later.