I love Ms. Rowling for writing her Harry Potter series, but I hate it whenever she does something like this. Stop teasing us, dammit!
The bane of every book collecting person: the Silverfish. DUN DUN DUNNNNN!!! How to get rid of them? If one book has been infected, place it inside an air-tight plastic bag along with some silica gel desiccant. The silica gel is important to get rid of moisture, because you will now place the sealed plastic bag with the book in it inside the freezer. Leave it in there for a couple of days so that those bugs catch their death of cold. If you're feeling particularly paranoid, (like I usually am) feel free to leave the plastic bag in there for a week. If they're not dead, then you might likely have an infestation of zombie silverfish , which is out of the scope of this blogpost. But what if a whole colony of silverfish decided to invade your whole bookcase? Then you have to make sure you're ready for war. Place a generous amount of silica gel (or if you can find it, diatomaceous earth) behind your books at the back of the shelves so that moisture levels remain low.