There are a number of books that mention the case but the only full length study  is  “The Trial of Elvira Barney” by Peter Cotes (1976). This has a full transcript of the trial and an excellent long essay by Cotes. Cotes met EB, knew Arthur Jeffress and others close to the case. Cotes was a theatre producer/director and brother to John and Roy Boulting.

Trial of Elvira Barney (Celebrated trials series)