The Magician's Nephew
by C.S. Lewis
Book one in The Chronicles of Narnia
Digory and Polly meet and become friends one cold, wet summer in London. Their lives burst into adventure when Digory's Uncle Andrew, who thinks he is a magician, sends them hurtling to...somewhere else. They find their way to Narnia, newborn from the Lion's song, and encounter the evil sorceress Jadis, before they finally return home.