The series takes place in the same universe as Cast a Deadly Spell
Detective fiction, parallel universe with magic... it just fits.- Except for the technology levels, which are at least at 1920s level (if not as widespread) in Spell, with automobiles and telephones, while such devices were never invented at all in Lord Darcy's universe.
- They have telesons in Darcy. Sorcery, not electronics, but they work.
One key reason the Protestant Reformation never took place in this universe is due to the fact that magic makes it possible to do much better screening for priests.
In our history, the Catholic Church was so plagued with corruption and scandals during the medieval era that it provided a major impetus for Martin Luther and other reformers in the early 16th century. In the universe of Lord Darcy, magical techniques make it possible to reliably identify moral/ethical failings and issues which would make a person unsuitable to be a priest, therefore, Saintly Church is the norm, as all priests and higher Church figures up to and including the Pope himself have passed this screening and are verified to be of sound moral character.