A Science Fiction Novel by Robert Heinlein published in 1958 . It had been previously published in serialized form in 1941 but was expanded for this novelization.
Introduces the Howard Families who have greatly increased their lifespan by selective breeding. Of course the general population think they have discovered the secret for longevity and want the knowledge themselves. The families are arrested and put in a camp where the information is to be extracted by torture if necessary. The familes escape and steal a 2nd generation starship to flee from earth. they return to earth 75 years later to find that the secret for longevity had been discovered.
introduces the character of Lazarus Long the oldest of the Howard Familes. ( in excess of 200yrs old at the start of the story).