Death at the Beggar's Opera is the second in the John Rawlings series by Deryn Lake. It's on sale for £0.99 and $0.99 at Kindle UK and US respectively. A lot of the later titles in the series have been on sale from time to time - it's nice to see a couple of the earlier titles on sale too (the first was on sale not too long ago).
Kindle US:
https://www.amazon.com/Death-Beggars...dp/B07KYL4QVF/
Kindle UK:
https://www.amazon.co.uk/Death-Begga...dp/B07KYL4QVF/