R Heilein's "Methuselah's Children" now.
Never heard of either. What is it about and is it any good?
Made a spelling mistake of course. Heinlein with a second "n".. Robert Heinlein
"Either"? Him and the book or the other book, Number of the beast?
Heinlein is an author that likes to interweave characters in and out of standalone but related novels. But his "Lives of Lazarus Long collection" (writen between 1958 and 1987) focuses around a long lived group of humans called the Howard Families. (One of) The primary character(s) is Lazarus Long who even among them has an exceptional life span. "Methuselah's Children (1958)", is set in a fairly typical futuristic earth (almost Utopian but with Dystopian undertones). The Howard Families (about 100,000 individuals) are revealed to the short lived but the others react badly thinking they have a secret "fountain of youth" which shouldn’t be denied to the rest of humanity. It is simply genetics however, yes basically inter-generational in-breeding. Heinlein acknowleges that the Howard Families have a higher tendency for abnormalities off set by longevity and / or special talents (although not all of them have abnormalities or special talents) but their long life does mean more life experience which is what they mostly rely on.
Any way after being relvealed they are forced to flee earth or suffer "scifi torture/mind control trickery" at the hands of the authorities/global government to get their "supposed” secret.
The other, "The Number of the Beast
" starts off in an alternate reality but ends up in the Methuselah's Children multiverse (at least it has some of the same characters at the end). The title references the supposed number of plausible universes in a 6 dimensions: 6 to the power 6, again raised to the power 6. This one is complicated enough but basically a scientist and family go universe hopping in a converted AI flying car called "Gay Deceiver" (No the name isn't explained). It's a fun story though.
"To Sail beyond the Sunset
” focuses on Lazarus' Mother and starts off in the 1800, in to the 1900s and onwards. It's interlinked with "The number of the beast" as it has some scenes replayed from her point of view with the same characters.
"Time enough for Love
" is really some of Lazarus Long's back story told in retrospective narrative. Basically he's so old that he wants to die but agrees not to kill himself as long as his companions will listen to his stories.
"The Cat who Walks through Walls
" is yet another (and yes has a cat that... er... does). This cat if I remember has the ability to basically appear where ever it likes and it is explained that Pixel (the cat's name) is too young to know that such behavior is impossible.