Dinosaurs Before Dark (Magic Tree House, Book 1) (by Mary Pope Osborne)

In the first of many Magic Tree House adventures, 8-year-old Jack and his 7-year-old sister Annie discover what they think must be the "highest treehouse in the world." They climb up and find it's filled with books. When Jack fingers a picture of a Pteranodon and says, "I wish I could see a Pteranodon for real," his wish comes true.

Jack and Annie are transported back 65 million years, where they meet a flying reptile they name Henry, a 12,00 pound flower-eating Triceratops, a duck-billed dinosaur with a voice like a tuba called an Anatosaurus, and a T-rex who could eat a human in a single bite. A mysterious gold medallion with the letter M is collected along the way, reassuring the two that their trip in the flying tree house was real.

In this first adventure, Mary Osborne sets the stage for her popular series. The set-up is inventive: A book must be found and opened and a wish made for the tree house to begin spinning -- and transport Jack and Annie to another place and time.

An escape, in which Jack hops atop an ancient flying reptile and soars over a Tyrannosaurus rex, will have readers holding their breath, then cheering for the hero's return to safety. And even though Jack gets to do the flying, Annie has her part: It's her ingenuity that saves her brother.