I just read the book again after watching the film version, and the changes are pretty noticeable. The biggest one is the entire ending. In the book, Cole's transformation is more internal, a long, painful process of confronting his anger and learning true humility from the Tlingit teachings and the spirit bear. The movie streamlines it a lot, gives him a more obvious, external villain to overcome—like that rogue logger subplot they added—which kind of undercuts the book's message about internal peace. The bear itself felt different too; in the book it's this almost mythical force of nature, while the movie, maybe because of budget, makes it feel more like a standard dangerous animal.
Also, they condensed a lot of Edwin and Garvey's roles. Their quiet, patient guidance in the book gets rushed, and some of the most powerful meditations, like the anger dance, are either shortened or cut. The setting felt less isolated and harsh as well. I get that adaptations need to make changes, but the core theme shifted from 'healing comes from within' to 'healing comes from defeating a bad guy'. It's still a decent family film, but it loses a layer of depth.