Ghost WarsThere is a certain category of books on history that I call "dense" because so much detail is packed into each page. Many times, I'll start a dense book but not finish, because the weight of detail isn't handled with enough skill by the author to avoid boredom. Recently, though, I finished reading Ghost Wars: The Secret History of the CIA, Afghanistan, and Bin Laden, from the Soviet Invasion to September 10, 2001, and if you want to understand Afghanistan, I highly recommend this book.
Ghost Wars is beautifully written by Steve Coll, who manages to pack the book with incredible density of detail without becoming boring. The complexities involved in the relationship between Afghanistan, Pakistan, Saudia Arabia, and the United States are explained in careful detail (very short verions: your friends are very likely your enemies in some way as well), and the recounting of events is meticulous, yet highly readable.
The subject matter is fascinating, the writing is terrific, and it's entirely without a political agenda, as far as I could tell. Coll has just done more work collecting information on what happened in that era than anyone before or since. Like I said, this book is seminal to understanding what's going on right now, so hit the link if you're interested.