Three individual titles in the latter half of Peter Tonkin's Richard Mariner series and one omnibus in the same series all have dropped to $0.99 and £0.99 each at Kindle US and UK respectively. All of them seem to be Kindle Countdown deals, good for about 5 more days in the UK, and about 5 1/2 more days in the US.
Red River, #23
Kindle US:
https://www.amazon.com/gp/product/B07KT5QLPP/
Kindle UK:
https://www.amazon.co.uk/Red-River-R...dp/B07KT5QLPP/
Benin Light, #19
Kindle US:
https://www.amazon.com/gp/product/B07LCLNX4F/
Kindle UK:
https://www.amazon.co.uk/Benin-Light...dp/B07LCLNX4F/
Ice Station, #24
Kindle US:
https://www.amazon.com/gp/product/B07KGB14YM/
Kindle UK:
https://www.amazon.co.uk/Ice-Station...dp/B07KGB14YM/
Ship to Shore, includes
The Leper Ship,
The Bomb Ship, and
Tiger Island (all of which have been on sale individually before)
Kindle US:
https://www.amazon.com/gp/product/B07DFNSRSR/
Kindle UK:
https://www.amazon.co.uk/Ship-Shore-...dp/B07DFNSRSR/