Most of Edward Marston's Railway Detective books seem to go on sale pretty often in the UK (in fact, most of Marston's books seem to go on sale in the UK fairly often), but this is the first time I've caught
The Stationmaster's Farewell, which is the ninth in the series, on sale. It has dropped to £1.99 at Kindle UK.
Kindle UK:
https://www.amazon.co.uk/dp/B007XF8GM4
Kindle UK/Smile:
https://smile.amazon.co.uk/dp/B007XF8GM4