Actually, I've read that putting the book in the freezer (in an airtight ziplock bag!) actually kills the bookworms (warmth and oxygen deprived). Leave it in for about 2 weeks.
For heaven's sake, get that book out of the freezer! Freezing temperatures and the moisture in the freezer can damage pages and bindings as much as bookworms! As a book seller my suggestion is to poke holes in your plastic bag ( take the book out first!) then place the book in a well aerated place (books need air circulation) and sprinkle dried lavender around the area in which you store your book. Insect pests seem to dislike lavender and it also helps to remove the musty smell old books develop!
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