What is a popular book that everyone buys but nobody reads?

there's entire chapters that just go "x is the son of y is the son of z is the son of a who's the son of b and the son of c".

I can't speak to how relevant this is to history in most parts of the world, but interestingly in places like ancient Ireland, genealogy was an important part of identity. Among the questions a stranger would be asked would be who his father is, what his clan is and what his profession is. Obviously today we value different aspects of identity, but historically at least in some places (and at the point I'm mentioning in history, Ireland was Christian) bloodline was part of how people knew you; it's a fascinating look into historical mindsets.

This is why you don't self-publish.

Sometimes yeah it's frustrating reading it because some parts assume cultural familiarity with very ancient names or places. I think I remember in the book of Genesis an ancient military leader is named and it's said he did some kind of trick to capture a town, but it doesn't explain what he did or why.

Storytelling has gone through a lot of development over the centuries

My partner bought a study Bible for academic use a few months ago, and our roommate bought herself one (for actual worship use) a couple weeks ago?