Major spoilers including surprise ending so come back and read later.
A thoughtful space opera, where we once again suspend disbelief and imagine a universe with faster than light drives and antigravity in order to perform thought experiments about a society kind of like the U.S. and its relations with countries kind of like terrestrial 3rd world nations. (Think drone-fired rockets tearing into a Yemeni village X infinity.)
Let's get right to ruining the twist ending: the main character, a mercenary, doesn't know that he's actually his evil half-brother. This explains much of the character's élan regarding violence, but after you've lived with him for many chapters, you can't accept that he would be capable of the sadistically cruel act against his family and human decency that constitutes his main repressed memory. Banks has prepared us for the effect such sadism would have on the character we think we're channeling but not for how the act squares with the life of the character we're actually channeling. We see the evil half-brother in some childhood flashbacks but he's not particularly evil. When did he become a flayer, exactly?
The vignettes of the merc's life (going forward and backward in alternating chapters) contain some enjoyable, short-story-like writing: in one of the best episodes, the ambivalent warrior tries to live the life of a simple, solitary beachcomber and ends up getting entangled with some local nomads, leading to, whoops, death and violence. Banks excels at Deus ex Machina situations where a primitive society's claustrophobic reality smacks up against those hellish drones from the sky (also called drones in his books), or even just the superior training and experience of an "advanced" outsider. This is a staple of TV shows from Star Trek to Firefly but well-imagined and -described by Banks. Examples in Use of Weapons include scenes where a flying, briefcase-sized drone annihilates a pack of desperados on horseback and later in the book, the same drone performs brain surgery on a stroke victim in a backwoods-planet's hospital. These scenes are meant to thrill but plenty about the book questions the wisdom of the "Western civ" stand-ins' flagrant, repeated violations of Star Trek's prime directive not to interfere in developing cultures. The directive of Banks' (literally with a capital-C) Culture civilization is actually to interfere, often, with lesser beings but to do it discreetly, through mercenaries. Hence their recruitment of the military genius headcase who is our main point-of-view character.