How long has the book been wet? Books wet longer than a couple days will start mildewing and growing mold. Once that starts, there is little you can do on your own.
You need a flat, hard space like a table. Spread newspaper to protect it and offer a little more absorbency.
You'll need plenty of paper towels and a couple of heavy books or a piece of wood and a brick to work as a press.
Stand the book up on its spine and let it air dry until damp. Do not use a hair dryer as it makes the pages brittle. Place paper towels between damp pages. Change papers every few hours until dry. Direct sunlight will yellow pages.
Press only once completely dry and only if your pages are wavy by placing a stack of heavy books or a board with weights on top.
If you are unable to restore the book on your own, freeze it until you can get it to a professional restorer.