At the beginning of the "Phantom Tollbooth" by Susan Nanus Milo gets a package and drives off to Dictionopolis because he is bored.
On his way to Dictionopolis he gets stopped in the Dol Drums where nothing happens but then the watchdog helps him get out of the Dol Drums
Here you go
Boh King Azaz and King Mathemagician fight and then the two princesses try and solve the kings problems and the kings banish the princesses.
Milo, Tock, Humbug, and Spelling Bee go to the royal banquet where they all eat subtraction stew and King Azaz gives Milo a box with all the letters of the alphabet which can form words to form words to overcome obstacles that may stand in his way.
Milo drives to Digitopolis so that the Mathemagician can agree so that Milo can go save the princesses and the Mathemagician says yes but the Mathemagician gives him a magic staff for his journey.
After a long journey, where Milo, Tock, and Humbug were chased by demons and other bad things, Milo finally gets to the castle in the air where then he saves the princesses with his box of letters and his magic staff and Milo becomes a hero.