The Phantom Tollbooth appeals to readers of all ages. In some ways, it's written simply enough that a young'un will totally get it. The clear plot involves a young hero, a magical voyage, the threat of danger, and the idea of rescuing beautiful princesses. These universal ideas are easy and fun to read about, and make the book a classic YA gem.
But not so fast: the book is full of complexities. It's overflowing with puns, plays on words, and allegories (check out "Symbols, Imagery, Allegory" for more on that). The closer you look, the more complex it gets. We'd bet that even Shmoop missed a few things. Yeah, that's right: even Shmoop.