PIE - Author's Purpose. Useful for discussing different types of "writers" (journalist, author, ad copywriter). Re: ads, useful departure for discussion of the purpose of ads ("to persuade you to buy something."
Author's Purpose lesson. Note: Fiction, fantasy, adventure stories are more that entertainment, "a spoonful of sugar" for didactic purposes. These genres are used by an author who wishes to engage the heart as well as the head.