Ever since we've started working on Colombia, I've been looking for a good single volume history of modern Colombian history. I read Marco Palacios' "Between Legitimacy and Violence," which reads a lot like many Latin American history texts assigned in college, with a lot of emphasis put on an CEPAL-like analysis of import and export trends shaping the political economy.
But for a great single volume at just over 100 pages that is up-to-date that will help you understand what you read in the newspaper, it doesn't get much better than Forrest Hylton's 2006 book, "Evil Hour in Colombia." It briskly surveys the 19th and early 20th century, but the bulk of the book is dedicated to the post-Violencia (1946) history, or the period that Colombia has been at civil war.
Importantly, Hylton also shows how the paramilitary "demobilization" and the decline in killings and displacements in recent years are not the result of things getting better in Colombia, but rather of a more consolidated criminal control of the state apparatus. In other words, put Tony Soprano in charge of a government, and you'll have a criminally-enforced "peace." (As James Vega shows in a piece for The Democratic Strategist, such tactics can often just postpone more civil war.)
There are some shortcomings of the book, mostly having to do with the length. Some characters and their importance aren't explored in great detail. For insance, while Hylton sets out to correct the shortcoming of other histories that "give short shrift to radical popular movements," key moments in popular history like the struggle to create a unified Afro-Colombian movement in the 1980s through today, are scarcely mentioned. But these defects are more than made up for by the brilliant synthesis of material related to civil-military-narcotrafficker relations.