"Le Chevalier du Poulailler" is the first of a trilogy. It is followed by "Cotillon II" and "Le Comte de Saint Germain". It's an engaging mystery which takes place in 1745 France and uses historic characters like Louis XV and Antoinette Poisson, later the Marquise de Pompadour. It adds the dashing Chevalier du Poulailler, a Robin Hood who steals from rich scoundrels who deserve it.
Adding to the spirit of mystery, the Internet Archive copies of "Le Chevalier du Poulailler" and "Cotillon II" present a puzzle to the reader. The second halves of the two scans are swapped at page 97 in the text. So when you read "Le Chevalier du Poulailler", at page 97 you must switch to "Cotillon II" for the rest of the novel, and vice-versa.
Alternatively, you can download for free a complete 1864 edition of "Le Chevalier du Poulailler" at gallica.bnf.fr. However, Gallica doesn't have the two other volumes. I think the texts of the 1864 and 1906 editions are the same.
When reading "Le Chevalier du Poulailler", I recommend having an old map of Paris handy. Most of the streets in the novel have changed, mostly by Baron Haussmann, so a modern map of Paris will be frustrating. gallica.bnf.fr has some wonderful downloadable Paris maps drawn by Jacques Esnault. Look for "Nouveau Plan routier de la ville et Faubourgs de Paris" from 1780 or 1785.