When I read these stories of bibliophiles and their stacks, I really wonder more about their book flow. How many are they bringing in, processing (reading, skimming, reviewing, studying, etc.), and then what's the output look like. Are they selling them back, donating, or dropped back off at the library.

I used to buy a lot of books. Library book sales were fun - returning with boxes of books. These days I leverage interlibrary loans and reservations to a couple thousand titles a year, but only need a couple of shelves for any given week. My flow is steady and adaptable to the content. Notebooks, Zettle card / bookmarks, and plain text files for deep dives. And straight to trading platforms for certain magazines like BottomLine.