SOLVED. A book about a kid who reads an old fantasy book and has to name a princess at the end [s]

[Cora]

A kid whose mom died finds an old book at a library. He decides to read it in a closet at his school during class. After being locked in overnight, he decides to read the whole book. In the book, a boy is in a fantasy world where he has a horse and is set out on a quest to find an old tortoise. There are a lot of different people he meets and adventures he goes on. He finds this turtle with his horse, but he is not very helpful and the horse dies in the swamp surrounding the turtle. The people in this world have an emperor, who is going to become a father but does not know what to name his daughter. The people in the book begin to ask the boy reading it to name her. They boy thinks this must be a coincidence that they are asking someone with his name who does not seem to be in the book to name this girl, but as the book goes on, the whole world is falling apart and he must name the girl. He leans his head out of the window of this school closet and shouts his mother's name and the characters thank him, through the book. I read this book several years ago and really enjoyed reading it. I would love to know what it is called so I can recommend it!

[Serendi]

The Neverending Story by Michael Ende perhaps?

[☆Joycedale☆]

That's not the neverending story is it? Was that a book?

[☆Joycedale☆]

O I guess it is a book lol

[Laina]

Ha ha, I didn't realize that was a book either! It sounds like the movie was pretty true to the book. Count me as a third vote for the Neverending Story.

[Ficie]

It is The Neverending Story for sure. The plot the OP remembers is only the first half of the book, which is also the part that was made into a film. The book does not finish there though, the characters go through many more adventures.