By Robert House. Foreword by Roy Hazelwood (yes, that one). I understand the skepticism that greets claims like "the only realistic and convincing solution to the notorious mystery of Jack the Ripper," not to mention the term "Ripperologist," which...it's all just kind of tiring. House's book is legit: well written, doesn't disappear up its own dupa with dead-end theories about minor dukes. I'm sorry it took me this long to stock it, but it's here now, new from the warehouse in paperback.
(The current copy got sliiiightly dinged in transit so I've knocked down the SRP.)