I want to buy some physics and math books, my parents gave me 2500 dollars to spend on books I want. Non-textbooks preferable. I want to read books that cover material that won't be covered in physics and math classes in college. Example: By the end of college I will have completed the 3 calc and physics courses required + 8 math and 8 physics more advanced classes by the end of my undergraduate study. My question is: What are some decent books that aren't too basic but that won't cover material required for those courses(i.e non-academic but informative books). As long as the book has an explanation for the math involved I should be fine as long as it's not a "year x, course y for dummies" book which is what I want to avoid. All suggestions are welcome.