Bodies in a Bookshop, by R. T. Campbell
This is a fun mystery from the Golden Age of British mystery. R. T. Campbell wrote several mysteries during WWII, and I'm not sure if they all feature Max Boyle and the Professor, but certainly it sounds like this is part of a series. They are an oddball little team, orthodoxly eccentric amateur detectives and pretty funny.
Max Boyle is a botanist, assistant to Professor John Stubbs. The professor loves a good mystery, and for some reason the local Chief Inspector invites him along on his investigations and even asks his opinions. (Sounds legit.)
Anyway, Max is the sort any bookish blogger can love, and one day while he's browsing in a favorite bookshop, he finds the owner and a stranger mysteriously dead in the back room. Max, the professor, and Inspector Bishop are promptly vaulted into a puzzle that winds through many a back room of a bookshop or print gallery. It's a very fun mystery.
One detail about the author made me laugh; his real name was Ruthven Campbell Todd, and under the name Ruthven Todd he was familiar to me in a different literary form. When my daughter was little, she used to love to read Space Cat stories, which date from the 1950s and are complete cheeseball science fiction for kids. So here's a Space Cat picture for you.