Today, I realized that I had two more boxes sitting next to our shredder, with papers piled on top of them. When I opened those, I found one box completely filled with hardback and trade paperback books (including Ulysses!) and one with graphic novels.
There's no way I can fit all of those onto the residual shelf space. So we have to buy one more set of shelves. My thought is to use it for the graphic novels, which will take up just over 100 shelf inches, and put it in the bedroom. Fortunately we still have an unoccupied wall (other than the art, which is about 5' up, leaving room for a set of shelves). The problem is going to be finding a set of shelves that's the right size.
But at least we haven't lost any books.
Addendum: We've ended up ordering two three-shelf bookshelves from Home Depot, to be delivered next week. That's more shelf feet than we need, but we couldn't find a single set that had quite enough width. They're actual wood rather than "engineered wood," so they should last longer and look better.