The first two titles in the Geoffrey Chaucer series by Philip Gooden have dropped to $0.99/£0.99 each at Kindle US/UK, as Kindle Countdown deals, good for about 6 more days. The remaining two titles are not too badly priced as is at $3.99/£2.99, and there's also an omnibus of all four for $5.99/£4.99, if you want to get them all at once. These were originally published under the pen name Philippa Morgan, but I couldn't find much info on those editions - I'm guessing Gooden has gotten the rights back and is re-publishing them himself.
This is a lot of links, so if you want the non-Smile links, just replace the "smile" with "www" and there you go...
Chaucer and the House of Fame, #1
Kindle US:
https://smile.amazon.com/Chaucer-Hou...dp/B08DDD3JDF/
Kindle UK:
https://smile.amazon.co.uk/Chaucer-H...dp/B08DDD3JDF/
Chaucer and the Legend of Good Women, #2
Kindle US:
https://smile.amazon.com/Chaucer-Leg...dp/B08DV9ZNJH/
Kindle UK:
https://smile.amazon.co.uk/Chaucer-L...dp/B08DV9ZNJH/
Chaucer and the Doctor of Physic, #3, not on sale, but not too badly priced if you like the first two
Kindle US:
https://smile.amazon.com/Chaucer-Doc...dp/B08F7SN8G3/
Kindle UK:
https://smile.amazon.co.uk/Chaucer-D...dp/B08F7SN8G3/
Chaucer and the Vintry Ward Death, #4, also not on sale, but not too badly priced if you like the first two
Kindle US:
https://smile.amazon.com/Chaucer-Vin...dp/B08F7VCCFM/
Kindle UK:
https://smile.amazon.co.uk/Chaucer-V...dp/B08F7VCCFM/
Medieval Blood: The Geoffrey Chaucer Mysteries - omnibus of all four titles
Kindle US:
https://smile.amazon.com/Medieval-Bl...dp/B08FF2M31P/
Kindle UK:
https://smile.amazon.co.uk/Medieval-...dp/B08FF2M31P/