Well, looks like they put all three volumes of Feynman’s Lecture on Physics online! Well, volume 1 and 3 have been around for a while, but volume 2 has finally been posted.
What are they about? You might ask if you don’t know about this. Well, they are transcribed version of Feynman’s Caltech undergraduate physics lectures decades ago. Volume one is mechanics and thermodynamics, volume two is electricity/magnetism and matter, and volume three is quantum mechanics. If you want to read them, I suggest a background in algebra, calculus, vectors, differential equations, and linear algebra. You don’t need to know all of those at the same time, it depends on the area of physics you are covering, but at the very least if you don’t have algebra, you are dead if you read these books.
Overall, it covers a large portion of what physics is about nicely. Just remember that just because you read this book doesn’t mean you mastered the material. It takes doing actual problem sets in order to know how to apply these stuff.