I'm looking to do a guided independent study course at my college next term; the college doesn't offer physics beyond the introductory calculus-based sequence, which I've completed, and I'm not yet ready to transfer. The physics major sequence at the school to which I intend to transfer continues with thermal physics, modern physics, and a mathematical methods sequence. I'm hoping to get a little bit ahead in one of those areas (not terribly picky about which). I have a solid math background including multivariable calculus and linear algebra and will be taking differential equations concurrently. I will have access to two wonderful instructors who will be happy to help explain any sticky parts, so I can probably handle a book geared to upper-level undergraduates. However, I don't want to get too far over my head - I don't think I can handle books written at the graduate level. I'd prefer a book in more-or-less "textbook" format with problem sets rather than a reference-style book, since I don't want to have to ask my professors to write problems just for me. So, can anyone recommend a text in one of those three areas that they consider an ideal follow-up to the first-year introductory sequence?