I recommend Gregory Chaitin's book intended for a popular audience. It is short, and a good introduction to algorithmic information theory for non-mathematicians. Chaitin's Constant (Omega) is a non-computable number that is equivalent to the halting problem.

[0]: https://www.amazon.com/Meta-Math-Quest-Gregory-Chaitin/dp/14...

Well you haven't mentioned how much math you're familiar with. But I'll assume that you know school level mathematics and are looking to learn more about the math mostly used in computer science. Get Concrete Mathematics( http://www.amazon.com/Concrete-Mathematics-Foundation-Comput... ) by Graham, Knuth & Patashnik - It's based on the course taught at Stanford since 1970 & it's really really good. Another book I think you should get is Meta Math: The quest for Omega( http://www.amazon.com/Meta-Math-Quest-Gregory-Chaitin/dp/140... ) by Gregory Chaitin. It's not really a math course book, and is mostly the authors take on his favorite topics in math, but if you want to improve your thinking process then this book will definitely give you a different perspective.