I guess it’s the history embedded in classic lit which gets to me – this is the first full length detective novel of the Western world. It was published only three years after the death of Eugene Francois Vidocq, the first professional detective, founder of the French national police force (Sûreté Nationale), and grand inventor innovator of devices and methods.
Edgar Allen Poe was inspired by a news clipping about Vidocq to write the first detective story and Wilkie Collins based much of The Moonstone by on the Vidocq. Finally, Arthur Conan Doyle’s Sherlock Holmes was modeled on the criminal-detective.
Although the books are similar in many ways, Monsieur Lecoq is quite a lot easier to read than Sherlock Holmes because the French is translated into more contemporary English – it’s an adequate translation.
And curious to note – Sherlock Holmes, in the introductory story of The Complete Stories of Sherlock Holmes, says he thinks Lecoq is a bumbler – it takes him way too long to solve a case – it could be a text book of what to avoid. That said, Gaboriau had a great influence on Arthur Conan Doyle, but Edgar Allen Poe (from 1841) influenced Gaboriau as well. These authors were almost all writing during the 1860s – their influence is felt even today.