Bats Fly at Dusk is the seventh in Erle Stanley Gardner's Bertha Cool/Donald Lam series. I actually like this somewhat lesser known series more than Gardner's Perry Mason books - the interplay between Bertha and Donald is really funny.
Bats is on sale right now for $0.99 in the US, and it's discountable at Kobo, where coupon code Partners22 is still working as of this morning, and brings the price down to $0.60 - or even less if you have a Kobo VIP membership as well.
Kindle US:
https://www.amazon.com/dp/B09VRR528V
Kindle US/Smile:
https://smile.amazon.com/dp/B09VRR528V
Kobo US:
https://www.kobo.com/us/en/ebook/bats-fly-at-dusk-1