Three historical mysteries from vastly different periods are on sale right now.
Babylon Berlin: first in the Gereon Rath series by Volker Kutscher, $2.99, set in 1929 Berlin, I've wanted to try this series for a while, so I'm happy to see this one on sale
Kindle US:
https://www.amazon.com/dp/B075JNYDRJ
Kobo US:
https://www.kobo.com/us/en/ebook/babylon-berlin-1
Caveat Emptor, fourth in Ruth Downie's Gaius Petreius Ruso/Tilla series, $1.99, set mostly in Roman Britain, I really like this series, especially Tilla...
Kindle US:
https://www.amazon.com/dp/B004CYEE34
Kobo US (coupon/VIPable):
https://www.kobo.com/us/en/ebook/caveat-emptor
Sold Down the River, fourth in the Benjamin January series by Barbara Hambly, $1.99, set in 1834 New Orleans, I keep meaning to try this series, but haven't gotten around to it yet
Kindle US:
https://www.amazon.com/dp/B004IK8Q18
Kobo US:
https://www.kobo.com/us/en/ebook/sold-down-the-river