The Hobbit by J.R.R. Tolkien
It's been many years since I read this for the first time and what struck me is that I had completely forgotten it was written for children. Tolkien addresses the young reader directly several times, reminding them of something he's told them in an earlier chapter and that sort of thing. He never forgets the child reading the book. There are trolls and massive spiders and other scary creatures but they aren't dwelt upon and they are always quickly defeated. It's very much a child's story in which bad things happen but good wins in the end. The films are a different thing completely.
I love the Peter Jackson Hobbit movies, though even I think it was a stretch making three of them out of one little book. In true movie fashion, the scary parts are scarier, the spiders bigger and uglier and the trolls more disgusting. The battle of the five armies took about 20 minutes to read in the book and three hours to watch on screen. The movies exaggerate everything, (what else would one expect?) bringing in characters that Tolkien didn't put in the story and even adding a romance. It seems every film must have a romance.
Fili and Kili are made more of in the movies than the book, and along with their uncle Thorin are turned into handsome Hollywood swashbucklers, which Tolkien probably never intended. (That's not a complaint - I appreciated Thorin Oakenshield's majestic swagger as much as anyone.) The book overall has a light touch appropriate for children that the movies discarded completely. There is lots of comic relief in the films, but they are weighty stories dealt with in a much more serious tone than that taken by the book. I have read that Tolkien's family dislikes the movies because they stray too far from the intent of the books. I can understand their point of view, but whether it's even true or not, who knows?
All I can say is I love the book for certain reasons and I love the movies for other reasons. I can't choose which I like better because I really don't see them as things that can be compared. They are different stories in many ways, different characters and types of characters, different tones and different target audiences. Both are wonderful and I love them all.