Why won't you have room for a book? Because that beach bag will need to be filled to the gills with snacks. No worse a time to be without a snack then while at the beach. Take it from someone who's walked (for what seemed like hours) down a beach boardwalk to find $15 hotdogs, while dragging two very hot and completely melting-down toddlers in tow.
Source: Flickr user jessebezz