Sacrilege! I would never look ahead in a book ( although I have been sorely tempted at times.) That would just spoil the whole line of the story. I do, however, have a habit of looking backwards while in the middle of a whodunit, to double-check facts. I like to try and figure things out before I'm told. (Almost never do)

I don't do it with mystery books, but usually I read the last couple of sentences of the last page...never gives anything away, and yet peaks my curiosity a bit.