In this extensive work, the authors give a complete self-contained exposition on the subject of classic function theory and the most recent developments in transcendental iteration. They clearly present the theory of iteration of transcendental functions and their analytic and geometric aspects. Attention is concentrated for the first time on the dynamics of transcendental functions to compliment the growing body of work on rational functions. The subjects covered in detail include the fixed point theory, basic properties of Fatou and Julia sets, components of Fatou sets, the geometry of Julia sets, and the Hausdorff dimension of the Julia set.