Written by Glenn Elert, this online textbook is aimed at "anyone with an interest in chaos, fractals, non-linear dynamics, or mathematics in general." Although it is not extremely technical, the author recommends having a decent mathematical background. Many people will recognize, at least by name, some of the topics covered. Mandelbrot and Julia sets are two well known fractals, and the book explains how they are constructed and gives some images. The fourth and final chapter discusses ways of measuring chaos. Some remarkable images of fractals are given in the Eye Candy appendix.