Here are some of his notable works:
Detective Novels:
* The Mystery of the Blue Room (1911): This novel introduced his famous detective character, *Monsieur Hire*.
* The Mystery of the Yellow Room (1911): Another popular novel featuring *Monsieur Hire*.
* The Mystery of the Golden Scarab (1912): This novel introduced another detective character, *Inspector Valério*.
* The Mystery of the Red Triangle (1919): Another novel featuring *Inspector Valério*.
* The Mystery of the Rue du Vieux-Colombier (1922): This novel featured *Inspector Valério*.
* The Mystery of the Vanished Jewels (1923): This novel also featured *Inspector Valério*.
* The Mystery of the Missing Will (1924): This novel also featured *Inspector Valério*.
* The Mystery of the Stolen Pearls (1925): This novel also featured *Inspector Valério*.
* The Mystery of the Hidden Treasure (1926): This novel also featured *Inspector Valério*.
Other Works:
* The Mystery of the Black Cat (1913): This novel was a mystery novel with a supernatural twist.
* The Mystery of the Crimson Mask (1915): This novel was a historical mystery novel set in the French Revolution.
* The Mystery of the Blue Diamond (1917): This novel was a mystery novel set in the French Alps.
* The Mystery of the Silver Key (1918): This novel was a mystery novel set in a country estate.
* The Mystery of the Haunted House (1920): This novel was a supernatural mystery novel set in a haunted house.
* The Mystery of the Lost City (1921): This novel was an adventure novel set in a lost city in the Amazon rainforest.
* The Mystery of the Stone Idol (1927): This novel was a mystery novel set in a jungle temple.
Magre was a prolific writer and wrote many other novels, short stories, and plays throughout his career. He was known for his suspenseful plots, intriguing characters, and detailed descriptions.