Around 55 cubic feet, or 2 cubic meters. That's about 20% over the capacity of our bookshelves, so we weed regularly but we also keep getting more books. On top of that I read about six full-length ebooks a month and another physical book from the library.
We buy some new but also swap books via the local mutual aid networks. All the ebooks I get from my friend Roger, he's very jolly. And Dolly Parton sends my youngest child a book every month because she's cool like that.
Even without the hot tub but especially with.