After Jack finds a mysterious blank book titled The Unusual Adventures of a Usual Boy named Jack, he's astonished to see that his mother's porcelain figurines have come to life. A little boy and a little girl want to hear of his adventures, and when Jack opens the book, the pages are suddenly no longer empty.

Another planet, blue trees, and little giraffes are just a few of the strange things that Jack sees in a series of fantastic trips. Traveling with assistance of the wind, of the wind, which gusts each time he puts on his magic backpack, Jack becomes an ambassador to other worlds. Along the way, he meets Lantorek, an elder of strange creaters-protaluxes, who describes protaluxes as "the most perfect creatures among all the beings living", and his son Maritolek, who doesn't measure his age in years; rather, he calls himself a "nine-rain boy" because rain-a very rare event in his land-has only occurred nine times in his life.

But when Jack travels to a planet where he is invisible, he meets Roco and Rici, twin brothers-clones, who urge him to leave the planet. If anybody finds his magic backpack, all three boys will be sent underground, perhaps to be trapped forever.

Brimming with magic, fantasy, and adventure, The Green Sky celebrates the wondrous joy of imagination.