Leave your book out in the rain? Drop it in the tub? Don't worry, you can fix it if you act fast.
This video, from the preservation experts at the Syracuse University Libraries, shows you how to get that sopping hardcover back into reading shape. To get started you'll need a lot of paper towels, a fan, flat boards, something very heavy and some patience.
Start by laying down a couple of paper towels, placing the book on top, then placing some more paper towels over the cover. Press on the book gently to remove any excess water on the outside. After that, insert two fresh paper towels inside your book every 10 to 20 pages, about a quarter of the way through the book — like they're enormous bookmarks. Then gently press on the book to squeeze out some of that moisture. While you do this, however, be sure not to open the book more than 90 degrees. Otherwise you risk damaging the book's now brittle spine.
After you've gone through the book completely, carefully prop it up and fan out the pages. Point a large fan at the book and set it to low. Let it air dry overnight. The book will be completly dry come morning, but you'll still need to flatten out the pages. Stick the book between two boards and place some very heavy objects on top to press it flat. Let it be flattened for 24 to 48 hours and it should be good as new! But if you don't have time to fix it right away, they recommend you stick it in a plastic bag and freeze it so you can go through this process later. Time is of the essence, dear reader.