There are several mysteries in the US Amazon Local 100 books for $0.99 deal, mentioned in this
thread, including all four Oliver Pötzsch/Hangman’s Daughter books, a couple of Ed McBain/Matthew Hope books (
Snow White and Rose Red and
Mary, Mary) and some mysteries from Amazon’s in-house Thomas & Mercer publishing arm - depending on whether you call that self-pubbed or not. YMMV...the Thomas & Mercer ones I noticed included mysteries by Kay Finch, Diane Sawyer, Marty Ambrose and Carol Costa. I didn’t look exhaustively, so there are probably some others too.