“The World of Mathematics” by Mathigon is a free online eBook that explores a diverse array of math ideas in an accessible and visually engaging way. Taking advantage of the digital medium, Mathigon contains fun interactive components in each of its 30 sections, many of which are still in development.
I enjoyed the Symmetry and Groups page, which did a nice job of making the idea of group theory comprehensible. Similarly, the Fractal page did a nice job showing what the Mandelbrot set actually is.
