Best books to gain solid understanding in physics and math topics?

Without knowing what is your current level it is very difficult to suggest any book.

If you are talking about textbooks, it really depends on what topic you want to learn (Algebra, Calculus, Mechanics, Electromagnetism…).

If you want a generalist one, many colleges' choice has proven it's:

Physics for Scientists and Engineers

(the latest Edition is better of course) by Paul A. Tipler (Author), Gene Mosca

Conceptual Physics by Hewitt

http://www.conceptualphysics.com/