New author Judson Troop's debut novel, The Gatekeeper: Day of the Dinosaurs, is a fascinating giant of a tale for young readers. And by "giant," the author means to submerge young readers into a world of dinosaurs, Native American legends, time travel, and prehistory. Eleven-year-old Rickey Ellis has more to worry about than classroom bullies and school rivals. While he's on a fieldtrip to a curious museum built over a quarry filled with fossilized dinosaurs in northwest Colorado, he accidently unlocks a time portal. Once a closely guarded secret by a now long-vanished tribe known as the...