The fibres in the paper have distorted and warped due to being dunked in the bath hound.
Have you considered getting a bath tray. At least then if you doze of the book would be protected. 
A bath tray. Not had one of those for years. As an avid bath time reader (and not averse to a can of cold cider in the tub either) I may have to re-visit this bath time piece of hi tech.
