I read half of the Donna Leon novels (which I liked) and the series is a very clever and very faithful adaptation of them. The writers/producers/director(s) have been able to add small charming details (of everyday life, such as the special relationship between Elettra and Brunetti) that make it even better, and delete those not absolutely necessary and required.
The series, made by the Germans (and not by the Americans or the Italians)(Italians do not know the novels since they are not translated into their language, oh!) is very well produced : budgets were obviously high, the series was shot in Venice, Italy, which means they have not made fun of the spectators All key players - Germans - not only pass for real Venetians but are simply perfect, especially (Brunetti's) Uwe Kockisch (he seems to be 45 y-o but has actually 20 more, huh!). My faves are ...all women characters/actresses, yes !