Have Space Suit—Will Travel

1958 original edition

Have Space Suit—Will Travel is a science fiction novel for young readers by Robert A. Heinlein published    in 1958 as the last of the Heinlein juveniles. It was my first exposure to RAH,circa 1965, and I've been hooked ever since.
It first was serialized in The Magazine of Fantasy and Science Fiction.

 for a time during World War II, Heinlein  was a civilian aeronautics engineer working at a laboratory where pressure suits were being developed for use at high altitudes, so he brought lots of realistic detail to this otherwise fantastic flight of fancy.

from the Wikipedia entry:Like Heinlein's other juveniles, Have Space Suit—Will Travel is a well-constructed adventure story, but compared to many of them, it takes a more philosophical approach, examining what is noble and ignoble about the human race through a varied cast of characters that includes humans, aliens, and even a cave-man. The "What is man?" theme is also explored in another of his juveniles, The Star Beast, but there the tone is more comic and ironic, whereas Have Space Suit—Will Travel is heroic, and sometimes even tragic.

1971 paperback edition

1983 Paperback