Castle in the Air by Diana Wynne Jones

In which a humble young carpet merchant wins, then loses, the princess of his dreams

Far to the south of the land of Ingary, in the Sultanates of Rashpuht, there lived in the city of Zanzib a young and not very prosperous carpet dealer named Abdullah who loved to spend his time daydreaming. He was content with his life and his daydreams until, one day, a stranger sold him a magic carpet.

That very night, the carpet flew him to an enchanted garden. There, he met and fell in love with the beauteous princess Flower-in-the-Night, only to have her snatched away, right under his very nose, by a wicked djinn. With only his magic carpet and his wits to help him, Abdullah sets off to rescue his princess….