Here's a description of Pelagia from the second novel in the series, Sister Pelagia and the Black Monk:
When the traveler grew weary of knitting, she took up her reading, and she somehow managed to to pursue this activity not only in the peaceful railway carriage, but also in a jolting omnibus. She was reading two books alternately, one of which was perfectly suited to a pilgrimage - An Outline of Christian Morality by Theophanes the Anchorite. The other was a very strange choice - A Textbook of Firearm Ballistics: Part 2 - but she read it with no less care and attention.
I'm not exactly sure why I like this series, except that it has all the benefits of old-fashioned, 19th century narration (lots of exposition and told in decorous third person) but the benefits of a modern novel's plot (lots of red herrings, twists and turns). The first book in the series is Sister Pelagia and the White Bulldog and I would start there.