There's a lot you can tell about someone by just walking into the front room of their home. There's probably people whose job it is to study stuff like that. A room too clean means something, too messy means something else. A room full of dead animals on the walls, or covered in superhero posters, all mean something. Yesterday I walked into a house where one of the four walls was covered, floor to ceiling, with books.
That says a lot about the people who live there.
We have a library in our home, the biggest collection of books is in the loft where we school the kids, or used to until it became a shrine to Legos. There are bookshelves in each of the kids's bedrooms, but in our front room, we don't have a wall of books. Our house doesn't really lend itself to a wall of books, but it would cool is we could.
I did a little snooping in the wall of books, under their supervision, of course. I always like seeing what books people have (or don't have...) in their libraries. They had a system with kids and YA books in their own areas, classics in another area, Shakespeare in yet another. Makes it easy for someone like me who has never seen the collection to find something excellent to read.
You can tell a lot about a person by just walking into their front room. And if they have a wall of books, you don't need to be a scientist to know what kind of people they are.