Sorted in the order in which they were published.
A series of five books introducing a pioneer in the detective/mystery genre. Monsieur Lecoq is a genius detective created by Émile Gaboriau; arrogant, proud, a master of disguise, and known for deducing things that others cannot see. The character was apparently based on Eugène François Vidocq, a police officer who used to be a thief. Whilst the Lecoq books of Gaboriau were popular, that popularity declined with the emergence of Sherlock Holmes, even though Gaboriau's character was a huge influence on Conan Doyle, going as far as to get a mention in A Study in Scarlet.