Bargain @ 99 cents each for US-only from HarperCollins e-books (likely available in all the US stores, linkage goes to Kobo since that's where I spotted them; you can probably try getting them with the OmniLit 50% off Halloween rebate which GeoffR alerted us to in
his thread here):
There's actually quite a lot of mysteries, and I'm not going to bother SYKM-linking the author credentials, since these are all established trad-pub names. Sorry, also unsorted since they've also some sf/fantasy & other genres on sale and I'd like to get some posts before the deals possibly expire if they're meant for monthly turnover.
There's actually quite a lot of them at the 99 cent price point, so here's some auto-linkage to the imprint name, sorted by price and filtered by category over @
Kobo.
Also, if you're possibly looking to use up your more disappointing Kobo coupons, Open Road Media's $1.99 Halloween sale is still good through tonight and has a lot of spooky-themed mystery/suspense thrillers and true crime titles, which can be found via the link in gweeks'
alert thread.