The book explores one of Vonnegut's favorite recurring themes, which is his belief in our need to belong extended families and how they would be an adequate, larger and more useful substitute for biological ones.
The most endearing section of the novel, in my opinion, lies in its introduction, where Vonnegut candidly describes his beloved sister's death, which took place shortly after she had learnt of a train accident where her husband and children had been killed.
As for the novel's plot, it follows the relationship of a boy and his sister who grow up together in isolation from the outside world because of their unsightliness. The boy turns out to be seen as more presentable and is separated from his sister, who grows to resent him for his seemingly desertion. Through some twists and turns they successively reunite and separate and after a major catastrophe, the boy becomes president of the United States, his campaign being centered on the formation of extended families on a grand scale.