Jackson was the anti-Tolkien. The book and movie stories had the same character names, many of the same events, but otherwise were completely opposite. A few things off the top of my head, great and small:
Tolkien's books were primarily about the corruption of power, and showed that the Good and Wise avoided it. There's the Ring, of course, but also Gandalf traveled around motivating people, rarely showing any magical ability at all. Aragorn's sword was broken until the great test required it. Jackson glorified power.
Tolkien's magic and world were places of beauty, darkness, and art beyond human experience; Tolkien never visualized Sauron, who was left to our imaginations. Jackson's world was of commonplace, manipulative horror film techniques and action hero tropes.
Heck, Tolkien's Gandalf had supreme confidence (for good reason); Jackson's was an anxious old person. Tolkien's Aragorn was the epitome of duty and commitment, always putting life and limb on the line for it; Jackson's didn't want the job!