Written by an international leader in the field, this is a coherent and accessible account of the concepts that are now vital for understanding cutting-edge work on supermassive black holes. These include accretion disc misalignment, disc breaking and tearing, chaotic accretion, the merging of binary supermassive holes, the demographics of supermassive black holes, and the defining effects of feedback on their host galaxies. The treatment is largely analytic and gives in-depth discussions of the underlying physics, including gas dynamics, ideal and non-ideal magnetohydrodynamics, force-free electrodynamics, accretion disc physics, and the properties of the Kerr metric. It stresses aspects where conventional assumptions may be inappropriate and encourages the reader to think critically about current models. This volume will be useful for graduate or Masters courses in astrophysics, and as a handbook for active researchers in the field. eBook formats include colour figures while print formats are greyscale only.