There aren't that many book-bound characters I find sexy in themselves. I mean separate from any film or TV representation of them, and separate from the heroine (or others) finding them attractive. For instance Corporal Carrott, not sexy in himself (I think), but believably attractive to the other fictional characters.
I can only think of one or two characters I've really been struck by. Louis Moore, the poverty-stricken tutor in Charlotte Bronte's Shirley, a sadly neglected character. Zaphod Beeblebrox (the 'best bang since the big one'). hmmm I'll think of some more in a minute. Oliver Mellors.