I don't really have anything to add, I just love this book. I searched for "The NeverEnding Story" in this community, saw that there was no post about it and wanted to fix that :).
As a 30 something, the movie is part of my dna, but I never read the book sadly. May check it out soon though, I'm trying to get my 7 year old to read more with me atm. And that cover art is beautiful.
I thought about adding a warning about the movies... I find very hard to ackowledge they exist (half kidding :P). Not because they are bad, but they are sooo different from the book; it's sad for me that they are the reference for the name.
I'm not sure I would recommend the book to children younger than ... (?) 11-12 years old. Although maturity in this regard is very personal and subjective and I'm not the one to say who should read what.