I became interested in how numbers actually work recently. I want a source that covers number theory. Explaining how and why numbers react the way they do. A friend recommended Mathematical Proofs: A Transition to Advanced Mathematics.
I want to learn about the concept of numbers, how they interact etc. I am a high school student, but most college level material will be appropriate.
-- Also, in my search I have found Mathematics in 10 lessons: The Grand Tour, and Foundations and Fundamentals of Mathematics.
If anyone could confirm that those two resources are adequate, I would appreciate it, and other resources are still welcome.
P.S. I do not like the Khan Academy. His presentations do not... serve my needs.