Jack the Ripper: Light-Hearted Friendby Richard Wallace
This book (with an introduction by the notoriously gullible Colin Wilson) is the author's attempt to prove that Jack the Ripper was actually ... Lewis Carroll.
Yep. The guy who wrote the Alice stories.
Wallace's book is way more entertaining than those books that "prove" that Francis Bacon wrote the works of Shakespeare -- but a whole lot less convincing. (Besides, doesn't everyone know that Edward de Vere wrote Shakespeare's works?)
The sexual interests of Lewis Carroll were certainly out of the ordinary. But Jack the Ripper? You couldn't prove it by this book -- and neither can Wallace.
Don't let that stop you from reading his book, though -- it's an excellent illustration of Chesterton's claim that reason is not the first, but the last thing a lunatic loses.