When you have PhD students for parents there comes a time when you get dragged to the library. When one of those parents is preparing for comprehensive exams it's possible you could get dragged to the library, oh, I don't know, three times a week.
Today I discovered the way to keep Sam quiet in the library. I tell him the books are napping. His eyes get big, he puts his index finger to his lips, and he tiptoes while saying, "shhhhhhh."
Works like a charm.