Concrete Mathematics by Graham/Knuth/Patashnik is still a great resource on the kind of mathematics and mathematical thinking we need in CS, but I'm not sure if it is fully accessible with a high-school level of Maths.

To be perfectly honest, I doubt I would've ever gotten through college-level maths without being forced to do it, as it can be very frustrating and difficult in the beginning. Unless you are quite confident in your self-discipline and enthusiasm to learn maths, rather than books I'd recommend something interactive (online course, forums, challenges).

If you are interested in a starting point to learn mathematics that are relevant for CS, I'd start with propositional logic and boolean algebra, as well as proofs via induction.