Guilty by Definition by Susie Dent is just £0.99 at Amazon UK.
https://www.amazon.co.uk/dp/B0CLKZMD3T/
It's also at Kobo, of course, but currently showing £2.99. But you should be able to price match it and get it for £0.89 nett.
https://www.kobo.com/gb/en/ebook/guilty-by-definition-1
Susie Dent is a well-known (in the UK) lexicographer. This mystery novel seems to have got good reviews. I shall be interested to read it.