"This book includes the content of all four I Didn't Know That books PLUS one BONUS BOOK， I Didn't Know That Some Trains Run On Water， in ONE REALLY BIG BOOK! Features： $7.99 Sturdy case hardcover binding Cover treated with eye-catching foil， embossed， and high-gloss enhancements Question-answering segments， colorful illustrations， fun facts， and exciting projects! Content so engaging kids won't even know they are learning!"