Edward Marston has a bunch of titles on sale at Kindle UK right now.
Murder on the Lusitania, Ocean Liner #1, £0.99
Kindle UK:
https://www.amazon.co.uk/dp/B09B9D17W8
Kindle UK/Smile:
https://smile.amazon.co.uk/dp/B09B9D17W8
The Lions of the North, Domesday #4, £1.49
Kindle UK:
https://www.amazon.co.uk/dp/B08514B7CZ
Kindle UK/Smile:
https://smile.amazon.co.uk/dp/B08514B7CZ
The Foxes of Warwick, Domesday #9, £1.79
Kindle UK:
https://www.amazon.co.uk/dp/B08GP42MMZ
Kindle UK/Smile:
https://smile.amazon.co.uk/dp/B08GP42MMZ
The Stationmaster's Farewell, Railway Detective #9, £1.79
Kindle UK:
https://www.amazon.co.uk/dp/B007XF8GM4
Kindle UK/Smile:
https://smile.amazon.co.uk/dp/B007XF8GM4
Points of Danger, Railway Detective #16, £1.79
Kindle UK:
https://www.amazon.co.uk/dp/B079SWNSRR
Kindle UK/Smile:
https://smile.amazon.co.uk/dp/B079SWNSRR
Fear on the Phantom Special, Railway Detective #17, £1.79
Kindle UK:
https://www.amazon.co.uk/dp/B07RD4G8GV
Kindle UK/Smile:
https://smile.amazon.co.uk/dp/B07RD4G8GV