MetaFilter has a list of the 100 best mystery novels of all time, including links to a lot of the texts.

For stories appropriate for this time of the year, check out the Christmas book recommendations.

And if I may add a personal recommendation:
A few days ago I finished reading The Kite Runner by Khaled Hosseini. It had been recommended to me by a colleague, who’d read it (in German) with her students. I won’t say anything about the details of the book here because I think I enjoyed reading it especially because I didn’t know much about what was going to happen. I’ll just say that it is about two twelve-year-old boys who grow up in Afghanistan before it is occupied by the Russians.
I rarely believe the praise that is printed on the cover of a book, but in this case the quote by Isabel Allende seems spot-on:

“This is one of those unforgettable stories that stay with you for years. It is so powerful that for a long time after, everything I read seemed bland.”

This is truly one of the best books I’ve read in a while. You can read the first two chapters here.