My granddaughter, who is 11, loves to read. I'd like to get her a set of books but, I can't for the life of?

me, recall the name. Four children were left with an old uncle that they didn't even know. The four of them were playing hide and seek and the youngest one found a closet, and a whole new world behind the clothes. I saw the movie, and I'm sure she'd love to read the book, if it's even a book at all. I, myself, would love to read it. Can any of you kind people help me with the answer? If you do, I thank you in advance!!!?