Title pretty much covers it, but I'll elaborate and say that I absolutely love Cormac McCarthy's southwestern novels (The Border Trilogy in particular). The books are steeped in Mexican history and I would like to learn more about it, particularly the revolutions, to help my understanding of the text.
John Mason Hart's Revolutionary Mexico is very good, perhaps the standard text: it's been through a couple of printings, and is in paperback. It does a good job of sorting out all the different factions ( urban workers, landless peasants of Morello, etc.) that made the course of the revolution so chaotic.
Frederich Katz also has a very big biography of Pancho Villa. If you got the time, it explains a great deal about the Army of the North and the revolution in general.