"It is very welcome that the authors have made recent progress in this active area accessible to the community in functional analysis and complex analysis. The reviewer would like to recommend this book strongly to everyone interested in operator theory on Hilbert spaces consisting of holomorphic functions." (Michio Seto, Mathematical Reviews, August, 2016) "The book under review, written by two of the main players in the field, is a summary of the developments in the past fifteen years or so about reducing subspaces of multiplication operators on the Bergman space plus a few other closely related topics. The material is well organized, the presentation is smooth, and the mathematics is simply beautiful. I would recommend the book to anyone who is interested in the Bergman space and multiplication operators on it." (Kehe Zhu, zbMATH 1321.47002, 2015)

• Introduction.- Some preliminaries.- Cowen-Thomson's theorem.- Reducing subspaces associated eith finite Blaschke products.- Reducing subspaces associated with thin Blaschke products.- Covering maps and von Neumann algebras.- Operator-theoretic aspect on von Neumann algebras.- Similarity and unitary equivalence.