Dinosaurs Before Dark by Mary Pope Osborne
While playing in the woods, Jack and Annie discover a tree house way up high in a tree. They go up there to discover that it is filled with books! As Jack opens a book about dinosaurs, the tree house starts to spin and they find themselves in prehistoric times! Will Jack and Annie find their way back home?
This is a great tale for young readers. It is full of adventure and makes you want to read more! Good thing this is only the first book of many in the Magic Tree House series to keep your young reader's head in a book.