The Montalbano books by Andrea Camilleri (the first one “The Shape of Water” is my least favourite, so stick with them).
The Brunetti books by Donna Leon – set in Venice.
C.J. Sanson’s “Shardlake” series – Dissolution; Dark Fire; Sovereign; Revelation and Heartstone… set in the reign of Henry VIII
“The Name of the Rose” by Umberto Eco
Recently I’ve been enjoying Roman detectives – Steven Saylor’s “Roman Blood” etc, Lindsey Davis’ “Falco” books, and the “Ruso” stories by Ruth Downie.