“Fairy Tale” is good but it’s not King’s best work. It has some of his classic tropes I really like, such as portals to alternate worlds, and thematic similarities to classic literature (in this case, fairy tales). But it’s also a bit drawn out in parts. I periodically reread some of Stephen King’s books, this probably won’t be one of them.
An alternative King story that has similar themes that I’d highly recommend instead is “The Talisman”, which was cowritten by Steven King and Peter Straub.
They could’ve made this clearer.