This is my daughter's very favorite book. I loved reading P.D. Eastman growing up too. The story is quite simple. A boy gets a fish and is told how much to feed it and not to over feed it. But he does feed the fish too much and consequently out grows his dish, the bath tub then the basement. It's a fun story. My daughter never tires of it. It taught her that when we tell her not to something there is a reason why we say that.
One of my all time favorite books! A Fish Out of Water is about a boy who buys a fish and then disobeys the petstore ower's advice to only feed his fish "so much and no more. Never more than a spot. Or something may happen. You never know what!"