Begg, Paul. Jack The Ripper: The Uncensored Facts.
Begg, Paul, Martin Fido, and Keith Skinner. Jack the Ripper A-Z.
Sugden, Philip. The Complete History of Jack the Ripper.
Any of the above are excellent on the Ripper.
Evans, Stewart P. and Keith Skinner. The Ultimate Jack the Ripper Companion. New York: Carroll and Graf, 2000.
Includes essentially every known important document, with some small commentary. An important reference for Hosts.
Evans, Stewart, and Paul Gainey. Jack The Ripper: First American Serial Killer.
First presents the Tumblety theory and a fairly strong argument for it.
Fido, Martin. The Crimes, Detection, and Death of Jack the Ripper.
Martin has changed his mind quite a bit since this book, but isn’t likely to write another one until someone pays him for it. Accessible and well written.
Harris, Melvin. The True Face of Jack the Ripper
Dubious from an analytical perspective, but potentially valuable for the game because it takes an occult spin.
Kelly, Alexander. Jack The Ripper: A Bibliography and Review of the Literature.
Exactly what it claims to be. Very useful if you’re serious about the Ripper.
Knight, Stephen. Jack the Ripper: The Final Solution
Totally wrong in every way. A fraud. Cool, though. This is the Freemasons and Prince Eddy theory.