Dust and Shadow: An Account of the Ripper Killings by Dr. John H. Watson
Lyndsay Faye's first novel before she moved on to 1800's New York. A mix of Sherlock Holmes and Jack the Ripper is a difficult minfield of an idea to walk through. Lyndsay nails it. The right amount of reverance and insider knowledge of all things sherlock is evident. Couple that with well sprinkled factual ripper chronology and you get a clever sure fire thriller which only hints of what she is capable of as a writer.