I would have given this four stars, but I had an issue with the way the book was structured. The author seemed to be not clear about what she was writing-a historical mystery, social commentary about Nineteenth Century England, or an exploration of the evolution of the fictional detective. The narration constantly switched between these modes and grated on the nerves at times.
That said, the mystery is excellent (with genuine clues, red herrings and all): and Inspector Whicher is as enthralling as any fictional detective, especially with regard to the one vital deduction which points to the solution of the mystery.
I wish the author had structured the book differently, first giving us the mystery without any dressings and then analysing its social and literary impact. I feel it would have been more effective.