While there are many amazing math books out there that specialize in a particular branch, I tend to prefer generalist books that cover a wide range of topics.

It you want something that starts with the absolute fundamentals, What Is Mathematics? is a perennial classic. I think that one starts with addition and takes you all the way through advanced calculus.

If you want a comprehensive survey of nearly all major branches in mathematics written by some of the most prominent Soviet mathematicians, you’ll want Mathematics: Its Content, Methods and Meaning.

If you want more of a reference-style encyclopedia, The Princeton Companion to Mathematics is a good one.

If you want to build a solid foundation for math tailored to computer science, look no further than Concrete Mathematics, coauthored by Donald Knuth himself.

Tons, but it really depends on where you're starting. Is there anything in particular you'd like to learn?

Every time I've recommended Calculus Made Easy [0] it's been a huge success. The writing is lively and full of motivating examples, and it's an enjoyable read.

[0] https://news.ycombinator.com/item?id=17185577