I think it's a little strange that I was never recommended to read this book. I had no idea that the movie was based on a book at all, and when I did learn it, I was already several years out of college. In fact, this revelation was brought to me by a sidelong comments from a friend about how the author thought the movie was an abomination and ought never have been made.
So, to start, Michael Ende is German. The book he wrote is (le shock) in German. That's why this cover says "Translated by Ralph Manheim." I'm sure there are some jokes and things that are lost in translation, but that is the detriment to only speaking/reading a single language - at some point I'm going to end up reading a book that I won't be able to experience in its original form.
Maybe that's a bit like watching anime with English dubbing. You just miss some of the things that would have been funny or impactful because the thing I'm watching wasn't written/scripted in my language.
To get to the book itself, though, I'd say this one is a little longer than its pace could comfortably support. Toward the end, I was powering through because in spite of it being a little boring I wanted to finish. That might have been me, rather than a fault of the book itself, but that was the impression I had.
This book is divided into two major sections. The first half concerns the main character, Bastian, and the process by which he gets to the magical world of Fantastica. The second half is about what he does while he's there, and has a completely different tone.
Have you ever read a book or watched a TV series where the main character starts as kind of a jerk and unlikable, but gradually grows into a nicer person that you get attached to as they develop? This was the opposite.
In the final two or so chapters, I remembered why I liked Bastian in the first half of the story, and that makes sense because the second half was all about the detrimental effect of getting your way all the time without needing to work for it. The main character learned his lesson, but it was the sort of journey that was almost painful to read about because there's this sense we have as human beings that the development of a likable character into a jerk is unnatural.
I think that feeling of unnatural development is a powerful tool, but I found the experience unpleasant after a certain point.
I'll give this book a 4 out of 5 for a good message, an emotionally satisfying conclusion, and the guts to subtly turn the main character into a villain partway through the story.
If you like books like Stardust by Neil Gaiman or The Chronicles of Narnia by C.S. Lewis, this might be a good fit for you, featuring a child going to a magic world and coming back with a new understanding of what's important in life.