I don't know if you play rock or not, but Total Rock Guitar is the best book I've ever bought.

Written by the master Troy Stetina, it has a good portion of solos and riffs from all kinds of rock. From heavy to alternative to swing type, it has it all. It comes with a CD and a few of the songs already have solos, but it makes the perfect jam track library. Songs are fun to improvise solos over. :D