
I suggest the streaming miniseries based on this book adapt a verse from Isaac Hayes' "Theme from Shaft":
They say this cat Lazarus Long is a bad mother—
(Shut your mouth)
But I'm talkin' 'bout Lazarus Long!
(Then we can dig it)
Yes, I'm going to do a major spoiler: about three-quarters of the way through the book, our protagonist, the apparently immortal Lazarus, goes back in time a couple millennia, to 1916 Kansas City, the city of his youth. And meets his family of that time. Including his mother, Maureen. And… like Futurama's Philip J. Fry, he winds up doing the nasty in the past-y. (Unlike Fry, though, it doesn't appear that Lazarus is his own offspring. Apparently too fraught for even Mr. Heinlein.)
Anyway: this 1973 book marked the return of Lazarus Long, last seen in his 1958 novel, Methuselah's Children (which itself was based on 1941 stories in John W. Campbell's Astounding Science Fiction magazine). Lazarus is an early success of the genealogical longevity project carried out by the "Howard Foundation".
As this book opens, Lazarus, an actual two thousand year old man, wants to die. He's seen it all, done it all, lost too many friends and lovers along the way. But through a mixture of persuasion and deception, he's brought out of his funk, and rejuvenated. For (approximately) the first three-quarters of the book, he acts as raconteur, telling tall tales about his past, dropping aphorisms and advice. And then finishes up with a (literal) bang, finding himself, against his better judgment, in the World War I European trenches.
Caveat lector: I read this book back in the mid-1970s, but since then my taste for Heinleinian dialog has faded. And this book has a lot of it, page after page of characters yakking. Or doing an inner monologue. Discourses on genetics. Cybernetic personalities transferred into clones. But not a lot actually happening, until that last 25% of the book, which is pretty good, but too late.