Definitely, highly recommended book. Learned of it from Quammen's "Spillover"[0] (a great — if somewhat terrifying — book in its own right) mentioning it as a source in the AIDS chapter and it was a fantastic read. Note that Quammen released his own AIDS-history book this hear, "The Chimp and the River"[1] (haven't read it yet though I intend to).

Direct link to Jacques Pépin's "The Origin of AIDS" on amazon: http://www.amazon.com/dp/0521186374

[0] http://www.amazon.com/dp/0393346617/

[1] http://www.amazon.com/dp/0393350843/