The first few titles in Leonardo Padura's Mario Conde series used to go on sale fairly often. I haven't noticed them on sale as much recently, but now here is the eighth book in the series,
Heretics, on sale in both the US and the UK, and it's discountable at Kobo.
Note that there are a couple of editions of this - one by Farrar/Straus/Giroux and one by Bitter Lemon Press. It's the Bitter Lemon one that's on sale, with a yellow cover.
Kindle US:
https://www.amazon.com/dp/B01N0GG0T7/
Kobo US:
https://www.kobo.com/us/en/ebook/heretics-73
Kindle UK:
https://www.amazon.co.uk/dp/B083CW33MN
Also, the third book in the series,
Havana Red, is on sale for $0.99 in the US - and also discountable at Kobo. It's not on sale, at least as of now, in the UK.
Kindle US:
https://www.amazon.com/gp/product/B005DB3MEM
Kobo US:
https://www.kobo.com/us/en/ebook/havana-red-1