Here’s a review in The Year’s Work in English Studies (2016):

“J.P. Wearing’s epic series of reference books on the London stage has proved an invaluable resource for theatre scholars since it first started to appear in the 1970s. Covering details about productions at every major London theatre from the 1890s to the 1950s, The London Stage: A Calendar of Plays and Players eventually spanned sixteen volumes. The indexes have now been republished in two monumental editions, which retain the same chronological divisions into decades (1890-9, 1900-0, etc.) with related material. This new publication also includes four key indexes to aid information-gathering: general, genre, theatre, and title. While there has been the occasional quibble about discrepancies with production figures, Wearing’s work remains the most reliable and informative source on plays in London during the first half of the twentieth century, and many will find this two-volume edition of great help.”