I bought CD storage boxes, like https://www.amazon.com/dp/B000EFJY3U/ https://www.amazon.com/dp/B000EFJY3U/, and then used both the lid and the box to put paper

I bought CD storage boxes, like https://www.amazon.com/dp/B000EFJY3U/ https://www.amazon.com/dp/B000EFJY3U/, and then used both the lid and the box to put paperbacks in. Stored alphabetically, spine up. I then stuck those in cupboards. It is amazing how much more efficient this is for paperbacks than a regular bookshelf! And that reduced my problem down to one which a regular bookshelf could handle, albeit with some creative packing into the bookshelf.