The Wrath of Mulgarth (Spiderwick Chronicles Series #5)

Three ordinary kids, Jared, Simon, and Wallory Grace, have entered another world -- without leaving this one! Two remarkable talents, New York Times best-sellers Tony DiTerlizzi and Holly Black, have risked everything to bring this remarkable account to light. Five books -- one thrilling adventure -- the Spiderwick Chronicles!
Their world is closer than you think.