I'm starting to learn CS all over again at the old age of 40, and had the pleasure to rediscover mathematics thanks to:

- Discrete Mathematics with Applications, by Susanna Epp, or

- Discrete Mathematics and Its Applications, by Kenneth Rosen (both have the same content, choose the style that you prefer), and

- Concrete Mathematics, by our lord and savior Donald Knuth.

I don't plan on reading TAOCP anymore as I would be dead by the time I finish reading everything else, but those introductory books are very good for beginners.