Although he is a fan of the show, Montalbano creator Andrea Camilleri has openly stated that Luca Zingaretti's characterization differs somewhat from how he had originally envisioned the character. Camilleri poked fun at this in one of the books, where it's acknowledged that the TV series exists in the Montalbano universe. Specifically, Montalbano himself states that, unlike Zingaretti (who's also 11 years younger), he has a full head of hair.
While the geography of Vigàta and Montelusa in the books is based on Porto Empedocle and Agrigento, the series is shot primarily in the city of Ragusa.