The book is about Lazarus Long, the universe's oldest living person, who is tired of living and wants to die.
The book takes the form of several Novellas tied together in the form of Lazarus's retrospective narrative.
One of the stories is about a US naval cadet who was "too lazy to fail." A lengthy, western-style story about his days as a pioneer surprises us, being rather un SF fare for a book proclaimed as a SF classic. Each stands well enough alone, but taken as a whole, paint an uplifting picture of a man who truly is in love with life.
Lazarus had dozens of careers and identities on a multitude of planets. Yet he always found time enough for love.