A number of mysteries are part of today's US Kindle Daily Deal, some new-ish, some old, all at $2.99 each, none matched at Kobo US, at least as of now
A Fatal Grace is the 2nd in Louise Penny's awesome Chief Inspector Gamache series. If you've somehow missed this series, here's a chance to pick up an early title on sale!
Kindle US:
https://www.amazon.com/Fatal-Grace-I...dp/B0011UGLRY/
Death in St. Petersburg is the 12th in Tasha Alexander's Lady Emily series. This was on sale last month too, so check carefully before you buy.
Kindle US:
https://www.amazon.com/Death-St-Pete...dp/B06XWF7C35/
The Day is Dark is the fourth in Yrsa Sigurðardóttir's Thóra Gudmundsdottir series. I've read and enjoyed all of the books in this series over the years.
Kindle US:
https://www.amazon.com/Day-Dark-Thri...dp/B008BU71FI/
The Company She Kept is the 26th in the Joe Gunther series by Archer Mayor. I've read and enjoyed all of the titles up to about half-way through this series - some in DTB, and then also several where the rights appear to have reverted and reasonably priced e-book editions exist. It's sort of rare for later titles in this series to drop in price, though, so I'm happy to see this one.
Kindle US:
https://www.amazon.com/Company-She-K...dp/B00V35U1YQ/
Three titles from Macmillan authors I don't recognize...
A Season to Lie, second in the Gemma Monroe series by Emily Littlejohn
Kindle US:
https://www.amazon.com/Season-Lie-De...dp/B072DTQQJV/
Swiss Vendetta, first in the Agnes Luthi series by Tracee de Hahn
Kindle US:
https://www.amazon.com/Swiss-Vendett...dp/B01IA6NW96/
Almost Midnight, 10th in the Mike Bowditch series by Paul Doiron
Kindle US:
https://www.amazon.com/Almost-Midnig...dp/B07J4W75YK/