The Masterful Author's Guide to Uniting Story Structure, Plot, and Character Development
Ratings11
Average rating4.3
Very useful book on character arcs for a single novel with in-depth explanations and questions to ask/answer for positive arcs, flat arcs, and negative arcs. I thought the questions to answer about each section were the best parts, as they really get you thinking about your character, and learned a lot - particularly when she describes what a flat arc ought to be.
When it comes to writing character arcs through a series, however, look elsewhere.