Story with a plot twist: The girl who cried the Monster

The girl who cried the Monster is a story of R.L. Stein of the book collection known as Goosebumps. The story is about Lucy Dark, a girl a bit pestiferous who enjoy scaring his little brother Randy realting him about monsters. One day she goes to the library for give back a book about monsters to the librarian, Mr. Mortman, and they start to talk about monsters. When she comes back home realized she has forgotten her camera and she goes back to the library. When she arrives to the library she discover that Mr. Mortman is a monster, so she run away at home. When she tells everything to her parents they don't belive her so, to demonstrate that is true, Lucy decide to go back to the library and take a picture of Mr. Mortman. Unfortunately the flash is turned on and Mr. Mortman start running after Lucy. When she arrives at home Mr. Mortman turn back in human and asks Lucy to let him in. The parents decide to invite him for dinner and he accepted. When he arrives and asks what is on the menu, they answers that Mr. Mortman is on the menu. In fact in Lucy's family they are all monsters. So Lucy parents transform and eat the librarian.