Romola by George Eliot
A while ago I saw a docudrama on George Eliot's life and was inspired to slowly read my way through her novels.
This one differs from most of her work, being set in renaissance Florence rather than rural England. But it does share several of the same themes, including ill-advised liaisons, the foibles of the clergy, and secrets that come back to bite.
By coincidence, I started reading this overlapping with the book on Leonardo and Michelangelo, which contained a lot of Florentine history that was useful in understanding this as well.