Based on the series of children's horror fiction novellas, Goosebumps follow child characters, who find themselves in scary situations. Zach Cooper move from New York to the fictional town of Madison, Delaware. Their neighbors are Mr. Shivers and his daughter, Hannah, but when Zach tries to introduce himself, Mr. Shivers warns him to stay away from them.
The film doesn't try hard to make the case that Hannah's as "real" as anyone else despite being from a book, though it easily could have. That's Goosebumps's implicit premise when it comes to the monsters, after all.