Here’s another review:

This is an exhaustive resource that attempts to provide biographical information on more than 90,000 individuals working in or connected with British and American theater. An update of the compiler’s American and British Theatrical Biography: A Directory, with this edition Wearing has expanded the work and drawn on information from more than 130 sources and 500 volumes of work. Foreign-born actors that have made significant contributions to British and American theater are included as well. The author has been broad in his definition of “theater,” allowing the work to cover ballet, opera, circus, and music halls. For each biographical entry the following is provided: name, birth and death date (if applicable), nationality, theatrical occupation, and codes to sources where more information can be found. This book will be useful in academic and public libraries where theater students, writers, and theater historians will have access to its many treasures.
(American Reference Books Annual (ARBA)