Teenage boys -- Juvenile fiction. Human-alien encounters -- Juvenile fiction. Science fiction. Young adult fiction.

Teenage boys -- Juvenile fiction. Human-alien encounters -- Juvenile fiction. Extraterrestrial beings -- Juvenile fiction. Life on other planets -- Juvenile fiction. Science fiction.

Teenage boys -- Juvenile fiction. Human-alien encounters -- Juvenile fiction. Extraterrestrial beings -- Juvenile fiction. Slavery -- Juvenile fiction. Machinery -- Juvenile fiction.