The Misbehavior of Markets: by Benoit Mandelbrot (Author),

Benoit B. Mandelbrot is world-famous for inventing fractal geometry, making mathematical sense of a fact everybody knows but that geometers from Euclid on down had never assimilated: Clouds are not round, mountains are not cones, coastlines are not smooth. To these insights we can now add another example: Markets are not the safe bet your broker may claim.