The protagonist himself is forgettable -- in fact, he's a shapeshifter. His identity is questionable even to himself. All he has is that he's pretty sure it's better to be biological than mechanical, and that's what seems to hold him together.

However... the world. The Culture. The Mind. The World of the Dead. And dear god, the fight scenes. This is a book that justifiably made space opera interesting, not just by showing an actual war (where all the protagonists know they are eminently disposable) but by showing a world which is clearly and utterly beyond humanity.