The field of laser-atom interactions has undergone spectacular progress recently, due primarily to the advent of superintense laser radiation. New phenomena have been discovered over a broad range of frequencies, from microwaves to the visible, and to X-rays, which require novel theoretical approaches. This book contains a unique collection of overviews of the latest advances, written by some of the leading specialists. It is addressed to all those active in these fields, but it contains sufficient introductory information to make it useful for a more general audience. The book examines the effects of superintense laser fields on multiphoton ionization and harmonic generation; covers novel effects with ultrashort, subpicosecond laser pulses; features Rydberg atoms in intense microwave fields; and presents nonperturbative theories of laser-atom interactions, such as the Floquet methods and the time dependent Schroedinger education method.