I think it's because I watched the films first as a kid and had rewatched the first movie so many times. Since the first book and movie are very close I think it just wasn't exciting to me whereas later books have many more differences.
Oh. That makes sense. I watched the first movie so much I could recite every line before the characters did. 😂 I find myself watching the fourth movie first. I plan on doing a reread at some point.