Seventy-Seven Steps by Christopher Fowler

3rd in the Bryant & May Mystery series

Set in 1973, we learn the details how the pair first joined Scotland Yard's Peculiar Crimes Unit. The murders Bryant and May investigate more than fit the unit's mission to handle cases outside the norm—an elderly lawyer is found poisoned in a hotel lobby, apparently from a snake bite, while other victims are killed by toxic makeup and a starved tiger. The odd sleuthing couple find that these terrifying crimes are all connected with the strange Whitstable family, whose Victorian patriarch founded a bizarre group called the Alliance of Eternal Light.

This interesting series has a much darker Sherlock Holmes feel as the pair deal with mysteries with supernatural aspects.

Bk 1: Full Dark House
Bk 2: Water Room