The dark doppelgangers of Sherlock Holmes and Dr Watson are the vile Professor Moriarty and his sidekick Colonel Moran. This book (presented as a found document written by Moran) is a blackly comic tale of their ten year partnership running London's crime. The duo run into Irene Adler, carry out an elaborate revenge on a rival of Moriarty, fight a hound from hell, steal every cursed jewel known to man and take a final trip to a waterfall.
This is very enjyable. Moriarty and Moran are vile disgusting people but it is entertaining to read this inversion of the Holmes canon and it ends on an interesting ambiguous note.