Hilborn, R. C. (1994) Chaos and Nonlinear Dynamics. An Introduction for Scientists and Engineers. Oxford University Press. Oxford.
Very well set up introduction to the complete field of nonlinear dynamics at an advanced technical level but with little assumed prior background. Of particular interest is an extensive collection of annotated references.
Peitgen, H-O, H. Jurgens, D. Saupe (1992) Chaos and Fractals. New Frontiers of Science. Springer-Verlag. Berlin.
A momentous work, providing a highly didactic introduction to fractal geometry, chaos theory, and the relation between the two. The book is beautifully illustrated and contains lots of exercises.