The Sad Variety is the fifteenth in the Nigel Strangeways series by Nicholas Blake. Lots of titles in this series seem to go on sale in the US pretty often, but this is the first time I've spotted this one on sale.
Per
SYKM,
Variety was a finalist for a Gold Dagger way back in 1964 when it was written. I've read some other titles in this series and enjoyed them, but haven't read this one (see "first time on sale" above

). It has dropped to $0.99 at Kindle US as a Countdown deal, good for about 6 1/2 more days.
Kindle US:
https://www.amazon.com/dp/B07TXR94DB
Kindle US/Smile:
https://smile.amazon.com/dp/B07TXR94DB