Leonard Smith's Chaos (part of the Oxford Very Short Introduction series) will give you the clearest (but not too painful idea) of the maths involved... There's a lot packed into this little book, and for such a technical exploration it's surprisingly readble and enjoyable - I really wanted to keep turning the pages. Smith also has some excellent words of wisdom about common misunderstandings of chaos theory... One of the best books so far in this useful and informative series. (popularscience.co.uk
About the Author
Leonard Smith is Senior Research Fellow in Mathematics at the University of Oxford, where he lectures on nonlinear dynamical systems and chaos.