Several books in the Joe Gunther series by Archer Mayor are on sale one way or another. All are repeat on-sale, but if you are missing (and want) some in this police procedural series, these might fill in a hole or two. I read several in this series back in DTB days, and now have been rereading them slowly, and enjoying them again.
The Dark Root (#6) is at $2.99 on US Kindle Countdown for about 1 1/2 more day. Info in this previous post:
https://www.mobileread.com/forums/sho....php?p=3209771
The Ragman's Memory (#7) is at $0.99, unsure how long. Info in this previous post:
https://www.mobileread.com/forums/sho....php?p=3100413
Fruits of the Poisonous Tree (#5) is at $0.99, unsure how long. Info in this previous post:
https://www.mobileread.com/forums/sho....php?p=3060325
Bellows Falls (#8) is at $0.99, unsure how long. Info in this previous post:
https://www.mobileread.com/forums/sho....php?p=3028945
Gatekeeper (#14) is at $0.99, unsure how long. Info in this previous post:
https://www.mobileread.com/forums/sho....php?p=2939426