What are some good mystery books?

I’m kinda stumped on this. I’ll probably read most of them, but I’ll prefer a young main character (also older ones are fine) and ones that are set in modern times (again, books set in older times are fine too, but I just prefer it in modern ones as it add a lot of ideas to be explored). I don’t need it to be well-known or anything, as I’m pretty happy with some of the lesser known books.

Some of the books that I have read in/related to the mystery genre is: Agatha Oddly; The Famous Five; Sherlock Holmes; The Secret Seven

Thanks to you all in advance! 🙂 Also have a good day

by Moonlit-Easgle