The Spiderwick Chronicles

Jared Grace moves into an old house with his family, including his twin brother Simon and sister Mallory, that they’ve inherited from their great uncle Arthur Spiderwick. When bizarre things start happening on the estate, Jared finds a book that holds the secret to the mystery, which includes several strange creatures who lurk in the shadows.

It turns out that Uncle Spiderwick was the first person to write a field guide to the magical realm, just before he mysteriously disappeared. Eighty years later, the goblins who live in the forest outside the estate are still after the book, since it contains all the secrets necessary for their leader, Mulgarath, to take over the world. When Jared unseals the book and brings it too close to the forest, he re-awakens the goblins and has his eyes opened to the entire magical realm, both in and outside his house.