I think another key factor is genre. Maintaining a large collection of technical books takes up a lot of space and many of the books become outdated quickly.

I think another key factor is genre. Maintaining a large collection of technical books takes up a lot of space and many of the books become outdated quickly. Ebooks have the advantage of being "upgraded" at a lower price. However, books with many illustrations, photos, or even novels, do seem to feel better in their physical form.