Accretion is recognised as a phenomenon of fundamental importance in astrophysics. Accretion Power in Astrophysics examines accretion as a source of energy in binary star systems containing compact objects and in active galactic nuclei. The authors assume a basic knowledge of physics in order to describe the physical processes at work in accretion discs. The first three chapters explain why accretion is a source of energy, and then present the gas dynamics and plasma concepts necessary for astrophysical applications. The next three chapters then develop accretion in stellar systems, including accretion onto compact objects. Three further chapters give extensive treatment of accretion in active galactic nuclei, and the concluding chapter describes thick accretion discs. The second edition is a complete revision of the earlier account. In particular it gives much greater attention to active galaxies and quasars, where the accretion model is now accepted as the central energy source. The treatment is at a level appropriate for graduate students.