“Arthur Spiderwick’s Field Guide to the Fantastical World Around You” is a collection of notes and drawings about the world of faeries as discerned by its author, the Grace children’s great-great uncle (55). According to the guide, the strange activities inside the walls of Spiderwick mansion are due to a brownie, or its angry version, the boggart, tiny humanoid faeries who can help or hinder people. The children rely on the guide as they navigate the faerie world that surrounds them. As an instruction manual of sorts, the field guide acts as a plot device to explain otherwise inexplicable phenomena. It also reflects a trope in fantastical literature, where a hidden letter, book, or journal acts as a source of information.

Old and crumbling, the Spiderwick mansion is a Queen Anne–style Victorian house likely built in the late 1800s. Its three stories feature lots of dormer windows and a large central tower: “There were several chimneys, and the whole thing was topped off by a strip of iron fence sitting on the roof like a particularly garish hat” (2). Unsettling noises issue from the building’s walls; these creepy sounds launch the plot and entangle the Grace children in the beginnings of a grand adventure.