Write Characters Your Readers Won’t Forget is actually the first in Stant Litore’s writing series, though I looked at the one on worldbuilding first. It is even slimmer — about a hundred pages in a relatively small-format paperback — and makes for a fast read.
Though very different in form, shape, and style, it reminded me a bit of Lajos Egri’s approach. Litore asks us first about our character’s core strength, a characteristic that will enable them to face down some difficult situation and overcome it. Everything else — both their problems and the solutions to those problems — flow from that strength; just as in Egri’s view of drama, every situation and characterization has to flow from demonstrating the narrative premise.
As in Write Worlds Your Readers Won’t Forget, Litore provides a series of linked exercises for the reader, focused on brainstorming outward from these issues. After the initial task of looking at core strengths, he goes on to build up the reader’s skill in observation. There are exercises on noticing and recording physical sensations associated with emotion, and on developing dialogue style. Ultimately, Litore covers some of the same territory you might see in a more checklist-like approach to building a character bible, but the way he develops the priorities is important. It starts with the things that are likely to matter the most in creating a compelling story, and then allows the details to hang from those.