The author of this tome, Ralph Hone, complains that despite the various vignettes published by friends of Sayers and the previous full-length biographies, there exists "nothing like a balanced, critical biography" and he goes on to make the case that his is such a one, complete with references and footnotes and great swaths of quotes. And therein lies the strength of this biography - by quoting extensively from Sayers' letters, he gives a much stronger insight into her personality and views. Using Sayers' own words also have the added benefit that stylistically, Sayers writes better than any biographer. This book has a magnificent frontispiece in the form of a 1950 portrait of Dorothy L Sayers, painted by Sir William Hutchison, and the added advantage of photographs of Sayers throughout her life. 
 I have read 4 biographies of Dorothy L. Sayers to date: 
 Hitchman (1975) - Such a Strange Lady A biography of Dorothy L. Sayers 
 Dale (1978) - Maker and Craftsman 
 Hone (1979) - Dorothy L. Sayers A literary biography 
 Tischler (1980) - Dorothy L. Sayers A pilgrim soul 
 I'd recommend Hitchman (1975) for an easy-to-read overview, Hone (1979) for the more conscientious, and Tischler (1980) for details of Sayers' religious work.