Mirror Dance (Vorkosigan Saga, #8)
by Lois McMaster Bujold
I cannot read this entire book again. Mark's half of the story triggers my embarrassment squick something awful (he's terrified everyone hates him for fucking up, and he's basically right), and the last third of the book is incredibly graphic and inventive torture scenes. Or maybe it only felt that way when I was bravely trying to skim it. When I want to pick it up, I usually skip around to the Miles bits.
Maybe this is the reason I don't enjoy reading about Mark. Obviously lots of people disagree with me, though, and that's cool!