I believe that you're thinking of "The Twenty-One Balloons" (1947) by
William Pene du Bois.
The book is available from Amazon.com:
Various descriptions of the book:
"Professor William Waterman Sherman intends to fly across the Pacific
Ocean. But through a twist of fate, he lands on Krakatoa, and discovers a
world of unimaginable wealth, eccentric inhabitants, and incredible balloon
"Three weeks after leaving San Francisco in a balloon to fly across the
Pacific, Professor Sherman is picked up in the Atlantic clinging to
"When Sherman crash lands, nude, on Krakatoa, he meets its European
inhabitants. Because they are so incredibly rich (all due to Krakatoa's
diamond core) they spend their days inventing wild games and conveniences
while indulging in delightful foods and expansions of the mind. Pene du
Bois's original illustrations bring Krakatoa brilliantly to life while also
explaining the technical aspects of everything from balloon merry-go-rounds
to beds that change their own sheets."
"When he has a balloon accident, he lands on the small island of Krakatoa.
There he meets the islanders and learns of their abnormal ways, which
include a gourmet government, a volcano, and houses built on diamond
"He is greeted by friendly people and welcomed into the Krakatoan society.
Krakatoa's Gourmet Government and the strange inventions in many of the
houses fascinated Prof. Sherman. He also receives a share of HUGE DIAMOND
MINES! Nevertheless, Krakatoa is volcanically active."
Hot air balloons--Juvenile fiction.
Hot air balloons--Fiction.
Krakatoa - fiction
volcano - fiction