The Phantom Tollbooth by Norton Juster is a children's novel written in 1961. It begins with Milo, the young protagonist, spotting a mysterious package. When he opens it, he finds instructions for constructing a magical tollbooth. Once constructed, the tollbooth opens up to him a magical world in which he has adventures and is given a quest to rescue two princesses. The plot structure is that of a fantasy quest.
The protagonist of the novel is Milo, a young boy who is intelligent, but somewhat lazy and lacking in purpose. He is bored because he has no real sense of what he wants to do with his time and tends not to apply his intelligence until the magical world gives him a sense of purpose and direction.
Tock, the watchdog, is Milo's faithful companion in the adventure. He has the head, legs, and tail of an ordinary dog, but his body is an alarm clock. He gives Milo good advice, and is admirable character and good influence on Milo. The Humbug is Milo's second companion, and although he eventually proves himself a likable companion, represents false knowledge and an inflated sense of self worth. He has the form of a beetle.
King Azaz the Unabridged and the Mathemagician are the leaders of the fantasy world in which Milo arrives via the tollbooth. The Princesses Rhyme and Reason have been banished to the Castle in the Air; Milo's quest is to rescue them.