We found 2 Reddit comments about Theoretical Physics (Dover Books on Physics). Here are the top ones, ranked by their Reddit score.
When I was in high school, I learned from Georg Joos' Theoretical Physics. While it is a little dated (1934), it gives you a solid introduction to classical and quantum physics.
Also, you need to learn mathematics. Lots of it. It would be impossible to seriously explore physics until you have at least have a thorough understanding of multivariate calculus and linear algebra. If you only know bits of high school calculus, but are strong in geometry, I highly recommend Maxwell's Matter and Motion and An Elementary Treatise of Electricity.
$6 Theoretical physics
<3 doverbooks, anyway if you want mathematics + physics that's a good one to intimidate the laity with. Cheap enough that you can lend it out as well.