I can't recommend it because I haven't read it yet and I'm not a historian, but the book list has one book on Colombia. It covers a wider area, but it's worth pointing out if you're interested in the subject.

To the mods: I'm technically referring to the book list and not making a rogue recommendation, so please don't delete.

The Making of Modern Colombia: A Nation in Spite of Itself by David Bushnell (1993). A single-volume account of the history of Colombia best for those who want to learn the nuts and bolts of Colombian history. While certainly a multivolume approach would be preferable, the book should be a starting place for those who wish to become familiar with post-colonial Colombian history.

OT: I actually found this book yesterday at a flea market. I wanted to get it, so it was kind of remarkable.

Robin Kirk has done some really good work covering the history and dynamics of the conflict. I'd definitely check out "More Terrible Than Death: Drugs, Violence, and America's War in Colombia." I've never read his stuff, but i've heard that Steven Dudley has done some strong research and analysis from his experiences within Colombia. You might find his book "Walking Ghosts: Murder and Guerrilla Politics in Colombia." Good luck!