It looks as if someone (the author? someone else?) has gotten the rights to at least the first few books in the Lord Edward Corinth & Verity Browne series by David Roberts, which were previously published by Carroll & Graf. And right now the first three titles, issued by a new publisher, have dropped to $0.99/£0.99 each at Kindle US/UK. The fourth is $2.99/£2.99 and the fifth is on pre-sale at $0.99/£0.99.
Sweet Poison, #1:
Kindle US:
https://www.amazon.com/dp/B0DT21FRL9
Kindle UK:
https://www.amazon.co.uk/dp/B0DT21FRL9
Bones of the Buried, #2:
Kindle US:
https://www.amazon.com/dp/B0F1G457M4
Kindle UK:
https://www.amazon.co.uk/dp/B0F1G457M4
Hollow Crown, #3:
Kindle US:
https://www.amazon.com/dp/B0F3J4S8YP
Kindle UK:
https://www.amazon.co.uk/dp/B0F3J4S8YP
The More Deceived, #5
Kindle US:
https://www.amazon.com/dp/B0F8QLF7DK
Kindle UK:
https://www.amazon.co.uk/dp/B0F8QLF7DK
Also note that there used to be an omnibus of the the first four titles in this series that would go on sale from time to time, so check carefully before you buy. And of course, if you have the individual titles from the previous publisher, they won't show up as purchased on the webpage either.
As I mentioned five or six years ago (!!!), I read several of the early titles in this series in DTB, picked up on business trips to the UK, and enjoyed them, but the later titles were mostly a little too expensive in e-book for me. Maybe they'll come out at more reasonable prices now...