Heinlein also introduces us to a character that will pop up again in his latter writings.
We begin in the 22nd Century, but the roots of the story go back to Gold Rush era. Despite wealth, Ira Howard will die young and childless. But he creates a trust that states he'll financially support families who have long-lived grandparents. This desire to prolong human life has, by the 22nd Century, have over 100,000 Family members living well over 150 years.Despite Earth being somewhat of a utopian society, the idea that human life can be extended creates a conflict -many believe the Families lifespan induced by selective breeding is a ruse, and they have developed a secret method to extend life. Of course, the family possess no such rejuvenation device. To prevent a pogrom, Lazarus Long (the oldest member of the Howard Family it seems), proposes to their one supporter and the Families: hijack the colony starship New Frontiers, and leave Earth. Themes of the Bible also play into the story, as the first planet they discover turns out not be the Eden like place they hoped and are expelled when conflicts arise with the species that inhabit the planet. Then there is more issues with the second planet as well, that eventually puts the Family back on track to Earth. But for Long, who reveals his age to be somewhere around 241, decides that Earth is no longer his home and with the help of brilliant engineer Andrew "Slipstick" Libby -who built (with the group minds that occupied the second planet) that helped create the FTL drive that got them home 74 years after they left, decide to recruit other members of the Families in hopes of exploring space with the new drive. And to see what's out there.
As I said, there are a lot of ideas that the author puts out -from a Earth of the future that will be able to overcome war, prejudice, and famine ala Star Trek's Federation (and I suspect Gene Roddenberry got some of his ideas from this book) to the "magical" inertia device that removes mass to help space travel (along with the near faster than light travel). And long before it became fashionable for an author to tie everything to one single universe, this book (which began life as a serialized tale in 1941) falls into what John W. Campbell, Jr. coined as Heinlein's "Future History", a projected future of the human race between the 20th Century through the early 23rd (most of his short stories where written between 1939 and 1941 as well as 1945 through 1950 and complied into the 1966 book The Past Through Tomorrow). Although it seems Heinlein never fully intended to tie everything together (something that Isaac Asimov would eventually do as well) -he seemed to create a chronology of tales that fit together rather brilliantly.
Then there is the character of Lazarus Long, who will go on to appear in four other Heinlein novels. Which are now on my reading list of 2015 and on.