The Name of the Rose, by Umberto Eco is really good. It’s a mystery set in a medieval Benedictine monastery. A Franciscan is called in to investigate before the Dominican Inquisitors get there. Likewise, there is scheduled a debate between papal legates of John XXII and some Franciscans who were teaching that the Church could not own any property at all that the monastery is supposed to host.
So you get this mystery as well as deep philosophical and theological discussion in a real historical environment.