And a few more (my post was getting too long):
Gravedigger is the 6th (blurb) or 7th (
SYKM), depending on whether you count a book of short stories, in the Dave Brandstetter series by Joseph Hansen
link:
https://www.amazon.com/Gravedigger-D...dp/B00COWLZHE/
Frail Barrier is the 8th in the Urbino Macintyre series by Edward Sklepowich
link:
https://www.amazon.com/Frail-Barrier...dp/B00QN3526U/
The Veils of Venice is the 9th in the Urbino Macintyre series by Edward Sklepowich
link:
https://www.amazon.com/Veils-Venice-...dp/B00QN3528S/
Deadly Hall is a non-series title by John Dickson Carr (orig written as Carter Dickson)
link:
https://www.amazon.com/Deadly-Hall-J...dp/B00ISH780C/
Red Shadow, apa
Red Danger, is a non-series title by Patricia Wentworth
link:
https://www.amazon.com/Red-Shadow-Pa...dp/B01CTOTFSM/
Poison in the Pen is the 29th (blurb) or 30th (
SYKM) in the Miss Silver series by Patricia Wentworth
link:
https://www.amazon.com/Poison-Miss-S...dp/B00AG8HIZ6/
Again, no idea why, or for how long (usually short with Open Road), and some have been on sale/free before so check carefully before you buy....