LSAT Logical Reasoning:

A friend of mine is planning to take the LSAT, and I'd like to get her a book that can help her prepare for the Logical Reasoning section. That's the only section I'm interested in right now. Can anyone recommend a book that's worth trying on this, or tell me to stay away from certain books?

Other readers, I'm sure, would also find this helpful, so I've enabled comments; please post your recommendations there. Thanks!