I'm still trying to figure out of this is even better than Player of Games...
It's certainly very different - a lot more complicated structurally, and more of a character study than the straight up classic plot of the other novel. The main character's Zakalwe, a mercenary working for the Culture's Special Circumstances division. This means he gets his hands dirty changing the history of lesser civilisations while the Culture can stay squeaky clean. Two things become quickly apparent - Zakalwe's a military genius, and a sick, sick puppy. He's terrified of chairs, for one thing. And he has a recurrent vision of a boat, but he won't let himself think about that either. A great portrayal of a very damaged individual.
There are two strands to this book followed in alternate chapters. One details him being brought out of semi-retirement by his handler Sma for a new mission; the other works backwards through Zakalwe's life until you learn what the hell's wrong with him. You get little snapshots of his life - falling in love, discovering the Culture for the first time, going on a drug-fuelled dream-quest, bleeding to death on a desolate island, being decapitated by natives etc. Very episodic, of course, but it works very well at telling you more about this guy's warped psychology as you follow him through the more straightforward "present day" plotline. But all the time you're being drawn back into Zakalwe's past, and the demons you know lurk there. Nice little red herrings along the way, and the denoument doesn't disappoint.
For much of this book, it has a pleasing John Le Carre/Graham Greene feel to it. Secret agents, exotic locales, moral ambiguity, and damaged heroes who know they're not always fighting for the right side. My one - small - criticism is that the "present day" plotline looses a little steam and direction towards the end, although it soon picks up again. The rest of the pretty small cast of characters are also fun - Diziet Sma: a woman very comfortable with her sexuality, if not with the violence sometimes necessary in her line of work. And the requisite drone Skaffen-Amtiskaw, who's typically sarky, badass and enjoyable.
This is the perfect Iain M Banks book to read after Player of Games I reckon - a sneak peek at the ugliness behind the utopian veil of the Culture.