Amazon US has a deal going right now for mysteries and thrillers. From the splash page:
|Limited-time deal: Mystery and Thrillers for $4.99 or less on Kindle|
Deal expires 10/30/2022 11:59pm PDT.
Here is a link to the home page for the deal. I haven’t had time to look through it, but will come back and update if I find anything really awesome (IMO).