The Little Prince: The Planet of the Tortoise Driver (The Little Prince #8)

On this broiling-hot desert planet, only carapodes - wondrous giant tortoises - can safely move around and deliver mail and resources to the lonely cities perched far apart on rocky ledges. And only one person, Arobase, can guide the carapodes. When he decides to leave them to fend for themselves, the whole world starts falling apart...