Quittin' time

HTMLGIANT posed an interesting question last week: when is it okay to stop reading a book when you don't like it? Do you stop after a certain number of pages or percentage of the book? Is there a time limit? Personally I finish every book I start no matter how awful, but that's not out of some noble sense of obligation to literature or my own pride. It's because I'm a little bit obsessive, especially about finishing things. It's the same reason I always clean my plate even when I'm uncomfortably full or use a bar of soap until it disintegrates in my hands. I can't handle the psychic baggage of having some unclosed loop out there in the world, not setting something back to zero. The counter argument is that life is too short and we shouldn't waste our time doing unpleasant things, but I figure I have that part locked down anyway. Even a bad book is a welcome diversion.

So, when do you give up on a book, if at all?