Dinosaurs Before Dark

This is the first book in the Magic Tree House series, where Jack and Annie discover a tree house filled with books. A magical pteranodon takes them back to the prehistoric times where they encounter real live dinosaurs. Before Jack and Annie can find out where the tree house came from, it whisks them to the prehistoric past. Now they have to figure out how to get home before dark or risk becoming a dinosaur's dinner. This is their very first fantasy adventure in the bestselling middle-grade series.