Throwaway because I've told people this story before and it's pretty recognizable.
My school's library is open until around 2 in the morning for the idiots like me who don't do their essays until the last minute, it's a pretty small building and most of the books are in the basement area called the "Stacks". Just to give you a quick layout, there's the big main stairs that go down to the Stacks, a vending machine room, and the long hallway with four entrances into the Stacks. The Stacks are two really big rooms on opposite sides of the hallway with a huge amount of bookshelves and study desks lining the walls.
I was there around 11pm last year, it was a pretty research intensive essay so I was down in the Stacks working in one of the study desks so I didn't have to keep going upstairs and downstairs again. I had been there for maybe two hours and everyone except for a boy working a few desks down from me had left already. I was pretty zoned out by this point, it was an 8am class so I didn't have much time until it was due and I was sort of panicking, so it really pissed me off when I heard someone flipping through book pages really fast to make them do that loud whir noise at the other end of the room. I sort of ignored it for a while thinking they'd go away eventually, but they just kept doing it.
After about five minutes, I got sick of it and started to walk over to tell them to be knock it off. I get about three steps across the room and it just stopped. I sat back down and it was quiet again for like ten more minutes before the flipping pages noise started again, only loads louder, like they'd grabbed a huge book that time.
The boy started to get pissed off too and he stood up and started walking through the bookshelves trying to find them. It keeps going so I got up too and started looking around with him. It got really loud and it was pretty obvious where it was coming from by that point, so we started walking towards it, he was on one side of the shelves and I was on the other.
We walked all the way down the shelves. No one there. We hadn't seen anyone come in the stacks and we were on the side of the room with the entrances, no way could anyone have come in without us seeing them. The noise stopped again and we both just sort of slowly walked back to our seats, I assumed it was just a fan or something in the other room and I really needed to get my essay done.
We sat down and immediately the noise started again, it sounded like it was coming from right next to the guy's chair. He shoved his stuff in his bag, looked at me, said, "Fuck this" and took off. I was out of there maybe five seconds behind him. I still won't go back in the Stacks at night, even when there's other people down there. No essay's worth getting murdered by a weird book ghost.