The twenty one balloons

"The Twenty-One Balloons" is a novel written by William Pène du Bois. The story follows Professor William Waterman Sherman, who sets out to fly across the Pacific Ocean in a hot air balloon but ends up on the mysterious island of Krakatoa. There, he discovers a secret society living in luxury thanks to the island's diamond mines. The novel is known for its imaginative plot and whimsical illustrations.