This book contains a detailed account of the bigeometric calculus, a non-Newtonian calculus in which the power functions play the role that the linear functions play in the classical calculus of Newton and Leibniz. This nonlinear system provides mathematical tools for use in science, engineering, and mathematics. It appears to have considerable potential for use as an alternative to the classical calculus. It may well be that the bigeometric calculus can be used to define new concepts, to yield new or simpler laws, or to formulate or solve problems.