Finished all three books of
Dave Duncan's Renaissance Venetian amateur sleuth mysteries, starring Alfeo Zeno (no relation to the Greek philosopher), apprentice to Fillippo Nostradamus (yes relation to the quatrain-penning mystic).
These are technically filed under fantasy, since they're published by Ace, but they're very low-key fantasy where supernatural ability is uncommon and the most magical things that happen are scrying via tarot cards and not using demons as a get-out-of-jail-free-card because that's an extremely bad idea. Also, if Nostradamus and Alfeo step over the line from respectable astrology and acceptable clairvoyance to "witchcraft", they'll be burned at the stake.
Otherwise, they're practically indistinguishable from an otherwise conventional period detective series with well-incorporated research and a handy glossary at the back. All three books not only had a murder mystery to solve, but also some convoluted backstabbing Venetian politics to untangle, which were intertwined with the whodunnit in generally fairly clever ways.
The Alchemists's Apprentice, 1st in the series, was a good introduction to the cast of characters, but the whodunnit felt kind of overly complicated with too many players contributing to the game.
The Alchemist's Code improved on the beginnings, and would be worth reading for the how-to medieval cryptanalysis lesson alone. Happily, it's also got a clever plot with humorous moments in it.
The Alchemist's Pursuit, which looks to be the final book, is the closest to a conventional murder mystery, on the trail of a serial killer with a possible revenge motive against courtesans, with a personal motivation for the sleuth as Zeno's girlfriend is herself a
cortigiana onesta (the high-class educated
hetaira-type variety like
Veronica Franco), and thus in danger.
Highly recommended if you like clever period mysteries which are true to the background in historical flavour but original in reinterpreting setting details and have neatly intertwined political/personal plots, likeable characters, and a sense of humour. These are going on my "buy when the price drops to dirt cheap with Kobo coupons" list.
Well, if you do end up doing so, I think you won't regret it.