Use of Weapons is one of Iain Banks' 'Culture' novels, based around the idea of a vast society of humanoid do-gooders, who want to guide the primitive toward a better way of life.

Cheradenine Zakalwe is one of their employees, working in the branch known as Special Circumstances, he is sent into societies on missions to help or hinder whatever may be going on that Culture wants to influence.

Diziet Sma, his contact in the Culture, and the drone Skaffen-Amtiskaw, have to find Zakalwe and send him on another mission. Over the course of the novel we discover a great deal about Zakalwe, why he works for the Culture, and who he is. He is hiding a terrible secret, and only one person can give him forgiveness.

The novel hints around the secret, never quite revealing it, you think you know, but then you think you're wrong. This is a fascinating exploration of one man's experiences working for a more advanced culture and trying to make amends. There are very few books that can carry off a story with a twist like this one, and this is one of the best I've read.