From the flap:
"What to do about the Brumblitron? Prewytt Brumblydge, its inventor, must be found before it can destroy him or start an uncontrollable chain reaction which might unravel the world. Tyco Bass, the only one who really knows whether the Brumblitron is a danger or not, is far away from Earth. When they are asked to help in this desperate situation, David Topman and Chuck Masterson feverishly comb Mr. Bass's notebook for some answer to the problem of the Brumblitron and its inventor.
David and Chuck meet Prewytt Brumblydge under surprising circumstances, then once more he disappears. Now the search is on and the boys take off in their space ship for Lepton, a tiny satellite of Earth's. Here they are faced with the necessity of making a momentous decision which could mean disaster for them and the outcome of their search. Mrs. Cameron has written another space fantasy with all the suspense and scientific detail of her two earlier books, The Wonderful Flight to the Mushroom Planet and Stowaway to the Mushroom Planet."
Spanish language edition:
El Planetoide de Tyco Bass, Editorial Acme, Coleccion Robin Hood #186, 1972 (translation by Ariel Bignami; illustrations by Ernesto R. Garcia)
Louis Darling took over the art duties from Robert Henneberger for the third book in the Mushroom Planet series. By 1958 Darling was already a star in the field, having illustrated seven books for Beverly Cleary, including Henry Huggins and Beezus and Ramona. Darling was born in Connecticut, studied at the Grand Central School of Art in New York, and started illustrating children's books in 1946. He died of cancer in 1970 at the age of 53.