[vector_spaces]

I think A Mathematician's Apology is a good read, but if you're looking to learn mathematics there are probably better places to start.

If you want a cursory view of various parts of mathematics, you might prefer Courant's book "What is Mathematics?". Depending on your background and interest, there is a volume of books (available as a consolidated cheap Dover paperback) called Mathematics: Its Content, Meaning, and Methods.

I recently came across A Programmer's Book of Mathematics[0] -- I haven't read it, but the author is a developer and the content might be more appropriate if you're just starting out -- both of the other books I mentioned are older, and are really wonderful texts, but might possibly be overwhelming depending on your appetite and background.

Finally, if you're more interested in math that's relevant to software engineers, there's Knuth's book "Concrete Mathematics".

[synthmeat]

I'd second the "What is Mathematics?" and "Mathematics: Its Content, Methods and Meaning" recommendations, in that order. Both are very cheap, comprehensive, and in ascending rigour. After those, it's really dealer's choice, with "Concrete Mathematics" being of particular interest to computer scientist.

Additionally:

- "Princeton Companion to Mathematics" is really fun to have around for exploration

- if you're really really rusty with math, take a week or two with "Mathematical Handbook - Elementary Mathematics" by Vygodsky

I literally have all these on my desk at this very moment, what a fun coincidence.