I'm sorry, but if I don't like the quality of the writing in a book, I can't get past it. I just feel like my time would be better spent reading something written by a writer who is skilled at his craft.
This really only applies to novels, which I tend to read with the intention of being impressed by the craft and skill of the storyteller. If I'm reading an autobiography or something, I can concentrate more on the story being told than on the manner in which it is written.