Congrats on being accepted to the program. No idea about the best book, but one of the best things I did some time ago, was to log in to khanacademy.org, and s

Congrats on being accepted to the program. No idea about the best book, but one of the best things I did some time ago, was to log in to khanacademy.org, and started doing some courses to re-learn a few things. Even things from algebra I and II, and trigonometry were interesting to re-learn. Now I'm reading some GIS projection code, and watching movies on calculus & trigonometry to refresh on integrals, matrix calculus, and sine/cosine. Maybe try Khan Academy and check the textbooks for some CS programs in universities. Best of luck!