I would select books based on your interest. I find the Dover publications good because they are both cheap and slightly older, this means they are less focused

I would select books based on your interest. I find the Dover publications good because they are both cheap and slightly older, this means they are less focused on undergraduate monetisation (version hopping, not supply answers to problems, glossy print), and more focused on proofs and algorithms. You can see them here http://store.doverpublications.com/by-subject-mathematics.html http://store.doverpublications.com/by-subject-mathematics.ht.... I particularly liked Probability: A concise course, and Number Theory by George Andrews. Amazon used to have a great number of graduate preparation book lists which always included books such as Rudin's Principles of Mathematics Analysis, and Halmos' Finite Dimensional Vector Spaces. These classic maths books are brilliant but usually easier to understand if you already have some experience with the material. Final advice is to find a study partner as it can be hard to track how you are going and keep motivated, especially without the instant feedback loop you get with programming.