If I'm in that situation where I really hate the book but also really want to finish, then it's usually because there's that nagging mental thread of something left undone.

But I don't want to read it. I just want to be done with it.

What I need is closure, which means knowing how the key points wrap up and what happens at the end.

And so knowing that, I commit a crime against literature - I skim.

Normally I'd never skim, but it's far preferable to never finishing at all, and it ties off that unpleasant dangling thread, letting me be free and move on to something I might actually enjoy.