St. Peter's Fair is different from most other Cadfael novels. The entire book is bounded by the fair itself, and divided into sections accordingly. This sets an unusual pace for the books, where you're more away of the time passing, and I found it quite immersive. We see so much more of the town, the people in it, how they pass their time, what they eat, drink, and buy.

The setting of the fair (of course) is a great opportunity to introduce several new and colorful characters, but also creates some compelling tension between the abbey and the town. Although a happy ending is assured, the abbey is cast as somewhat uncaring and inflexible, which is quite different.

My favorite bit, however, is this big Welsh guy who keeps showing up and is very obviously a spy--but Cadfael seems oblivious to it. The guy keeps saying things like "boy, if I were a spy, this is what I would do" and Cadfael says, "gee, isn't that interesting!" Perhaps I'm misreading it, but I enjoy it as a fun running gag.