Nabb seems to me to be the progenitor of writers like Donna Leon. The Marshall Guarnaccia mysteries are not only stylishly written but they deal with topics which put Nabb ahead of her peers.
Rebecca H. (amichai) reviewed The Marshal and the Murderer (Marshal Guarnaccia, Bk 5) on + 368 more book reviews
Excellent mystery situated in Florence. If you like Georges Simenon's Maigret, Nabb's detective Guarnaccia is in that vein.