wrote more than just The Phantom of the Opera! He was a journalist until he began writing novels and ended up with several dozen detective novels. I read The Mystery of the Yellow Room, one of the first locked room mysteries ever written, and today I finished The Perfume of the Lady in Black, a sequel with it's own locked room crime. It is a bit hard to discuss this book as so much of the story stems from the previous novel.
The heroine of the first novel, Mademoiselle Stangerson, is finally marrying her betrothed. Rouletabille attends but doesn't stay to see the happy couple off onto their honeymoon. We then have a few chapters where we learn of Rouletabille's early life. When the villain from the first novel threatens Mme Stangerson again, Rouletabille meets up with them at a castle on the French Riviera. The preparations to make the castle impenetrable are impressive.
Like the previous novel, Leroux includes maps and layouts so that the reader can visualize everything and try to puzzle out the mystery. Setting this mystery in a castle helps the atmosphere. There is a real feeling of fear in this novel and you do expect the killer to jump out at any time. He's as cunning and brilliant as our detective and desperate to succeed.
Overall, i'd say a 5. I certainly didn't understand some of the motivations of the characters, not being French or born in the 1880s. It is a solid book but i will say the first was better.