I'm a 2nd year college undergrad who is very interested in physics. I'm in my 3rd semester of physics courses, currently introductory E&M, but I really want to learn more advanced physics as well, or at least enough to understand things at a semi-technical level. I posted this here because it really isn't one specific topic that I'm interested in, but it all. GR, QM, SM, and beyond. I guess I am looking for book recommendations for starters. I'm currently taking a Linear Algebra course, so I'm looking for somewhere between the pop-sci level of "The Elegant Universe" and "QED" (both of which I've read this past summer) and a full-on textbook. I'm not even sure if this stuff exists, which is why I'm asking. My university have a fairly extensive science library, so if the only thing above pop-sci are textbooks, by all means recommend some. Along with this I wanted to know what mathematics I should look into beyond differential equations in order to understand higher level physics. Like this summer I tried reading some of Einstein's technical work, but that didn't make sense to me yet (It was the selections from Hawking's "On the shoulders..." so if that should have made sense with a background in Calc, tell me and I'll just give it another shot, or seek a professor's help). Well, that ended up being a lot longer than I expected, but any advice/help is much appreciated.