Buy: A book that you can read time and time again. Usually the story and the artwork are both far superior to the average children's book; although occasionally one really outshines the other. As a parent, or someone deciding what to get for a friend's son or daughter, you can rest assured that these are the only books you should purchase at full price.
Borrow: These are good books that are missing at least one key component. Sure, you might find yourself reading it the first time and thinking "That was pretty good." Unfortunately, with each successive reading, you grow to resent it a little bit more. Eventually, it just sits in your house as a show piece or finds it's way to the bottom of some bin in your kid's closet. You'd be better served making friends with some parents down the street and trading a toy your little one has grown bored with for a rental of this book.
Donate: To me, books that fall in this category are responsible for the majority of parents who question how an eight-page book can cost between $5 and $20 and what criteria publishers use to commit resources to such a project. They might be OK to read once, but you immediately decide to never subject your child to that form of punishment again. Alternatively, you might hate the entire thing from page one, but find that your child likes the pretty colors and shapes enough to make the suffering tolerable. If your son or daughter likes to eat books, pull a selection from this pile.
Destroy: Few people know this, but Dante actually had a tenth circle he was too afraid to mention in Inferno. It was reserved for authors that create abominations like this. If you already have this book in your possession, I'm sorry, I really am. There's nothing we can do for you at this point. The only form of relief you can get is to take this thing out of circulation permanently. For all others reading this blog, make sure you are wearing a hazmat suit if you plan on walking within a mile of it.