Until she tips the bookcase back.

"W-wait what...what are you doing? Not under there, I'll get all dust--oof"

He feels the force of the shelf coming down, and while it doesn't damage his physical self much aside from being somewhat flatter, it knocks the breath out of him. Good thing he wasn't hardcover, or else he probably wouldn't be standing.

"...You could've told me you were going to do that!"