This volume is an introductory textbook on the science of planets within our own and other solar systems. The book begins with a description of the basic properties of the planets in our solar systems, and then moves on to compare them with what is known about planets in other solar systems. It continues by looking at the surfaces, interiors and atmospheres of the planets and then covers the dynamics and origin of planetary systems. The book closes with a look at the role of life in planetary systems.