AH. I finally understand. People who are passionate about Banks' culture novels truly love these books with great enthusiasm. Although this is the fourth of his novels that I've read (the third in this series of mostly stand-alone works), it is only in this one that I grasp that kind of excitement. The common praise for his writing finally makes sense to me: in this book, the ship names are indeed utterly hilarious, and the AIs are deliciously snarky. Moreover, the culture's ulterior motives of being seemingly sinister for your own good are all too obvious.
Cheradinine Zakalwe hails from a backwater (non-culture) planet and has a robust military career. As a result, he is of use to the culture as an operative when the need arises - apparently, "utopia spawns few warriors." He is deployed to planets not quite ready for absorption into the culture to nudge wars in the direction determined to be best (though he often has no idea who is supposed to win or why). He is a battle-hardened warrior, gifted in the "use of weapons" - including diplomacy, generalship, assassin-craft, as well as guns and ammo - and he himself is a weapon used by the culture.
Zakalwe is (so far in my reading) Banks' most identifiable and "standard" protagonist - the blurb above makes him sound like a Michaël Bay movie action hero, and in many ways, that's true. However, Banks turns much of this trope on its head, and the story is ultimately more about personal cost than about huge explosions. Additionally, because he is an outsider to the culture, this book can serve as an excellent introduction to the series.
As a random aside, Banks is the author who now has the distinction of appearing most frequently on my personal "wow WTF" shelf - three out of the four books of his that I've read. So, take that as you will. It's a rare tale indeed that will have me literally gasping aloud with surprise (or shouting shocked expletives, good or bad) at a genuinely, thoroughly unexpected moment in the story. I haven't been a fresh-eyed teenage reader for many years now, so I really appreciate it when an author can actually shock or surprise me. But of course, your mileage may vary. Banks can be rather gory in those moments.