Several books e-published by Hard Case Crime have dropped to $2.99 at Kindle and Kobo US. Most (all?) have been on sale before.
Top of the Heap by Erle Stanley Gardner (Cool and Lam series)
Kindle US:
https://www.amazon.com/dp/B004V4FP4W
Kindle US/Smile:
https://smile.amazon.com/dp/B004V4FP4W
Kobo US:
https://www.kobo.com/us/en/ebook/top-of-the-heap
So Nude, So Dead by Ed McBain
Kindle US:
https://www.amazon.com/dp/B00ONTS4AC
Kindle US/Smile:
https://smile.amazon.com/dp/B00ONTS4AC
Kobo US:
https://www.kobo.com/us/en/ebook/so-nude-so-dead-ebk
Forever and a Death by Donald E. Westlake
Kindle US:
https://www.amazon.com/dp/B01M14UOWL
Kindle US/Smile:
https://smile.amazon.com/dp/B01M14UOWL
Kobo US:
https://www.kobo.com/us/en/ebook/forever-and-a-death
Sinner Man by Lawrence Block
Kindle US:
https://www.amazon.com/dp/B01BRFN652
Kindle US/Smile:
https://smile.amazon.com/dp/B01BRFN652
Kobo US:
https://www.kobo.com/us/en/ebook/sinner-man
These are just the ones who popped up on my eReaderIQ author feeds this morning. There may be more HCC authors on sale, so if you have a favorite HCC author, now might be a good time to look.