"The second great moment is when it actually becomes a book—a physical thing. I always feel that when you put a book into proofs it gets better just by virtue of being set in print. I know a lot of writers feel that way too. It takes on a kind of permanence. And then it's even more satisfying when it becomes an actual book."
As I've said before, I'm not entirely convinced by that last claim (post-publication depression seems comon, like post-dissertation depression), but I share the sentiments about page proofs.