Literature that one would take to the shitter, hence the term. Sunday funnies, album notes, and yearbooks are all good examples because they tend to distract from the dank smell of your feces. Shitterature usually does not include novels or any other piece of literature that requires concentration.

When you eat dirt for the first time and leave your family to build a shack in the woods

Any form of literature used to entertain yourself while shitting.