It’s a mystery
Edgar Award (Mystery Writers of America)
Search for winners in the Best Young Adult category.
Guess Again: Mystery and Suspense! (YALSA Popular Paperbacks list)
Mysteries (Teen Booklists, Seattle Public Library)
Adult Mysteries for Teens (YALSA Popular Paperbacks list)
Case Closed (good mysteries from Booklist magazine)
Mysterious Life(four good mysteries from NYPL blog)