The Circular Staircase by Mary Roberts Rinehart is considered a classic in the mystery genre and has significantly impacted the development of the genre as a whole. Here are some ways in which the book has influenced the mystery genre:

1. The “Had I But Known” trope: The Circular Staircase is credited with popularizing the “Had I But Known” trope, where the narrator laments a decision they made that ultimately led to the mystery or crime they are trying to solve. This trope has since become a staple of the mystery genre.
2. The “country house” setting: Rinehart’s use of a country house as the setting for the novel has also had an impact on the genre. This setting has become a classic element of the cozy mystery sub-genre, where the detective investigates a crime in a closed setting with a limited number of suspects.
3. Strong female characters: The Circular Staircase features strong and independent female characters, including the protagonist, Rachel Innes. Rinehart’s portrayal of women as capable and resourceful characters helped to pave the way for other female protagonists in the mystery genre.
4. Complex and layered plots: Rinehart’s use of intricate and layered plots, including multiple twists and turns, was groundbreaking for the mystery genre at the time. This style has since become a staple of the genre, with authors often striving to create equally complex plots.

In summary, The Circular Staircase has had a significant impact on the mystery genre, influencing everything from using certain tropes and settings to portraying strong female characters and the complexity of plots. Its legacy continues to influence and inspire mystery writers today.

You can buy The Circular Staircase on Amazon here.