It makes sense for me too.
When I was a student, I had to pass some competitions, only a few students were selected for the degree. And so, a lot of students were hiding the books needed to study the exam, among the other books of the library, on the wrong shelves, of course (as they couldn't take them outside of the library). In a big university library, it's very efficient to hide a book among other books.
It's impossible to find out. An excellent hiding spot, definitely better than to hide them among wares or food.