"The Mystery of the Yellow Room" by Gaston Leroux is a classic locked-room mystery set in France. When Mathilde Stangerson is found in a locked room with no apparent way in or out, journalist Joseph Rouletabille is determined to unravel the mystery. Leroux's tale is renowned for its suspenseful plot, clever twists, and exploration of themes like deception and truth. It's a gripping story that keeps readers guessing until the end, making it a seminal work in detective fiction.