There are several differences between popular literature and classic literature. They include differences in authorship, purpose, audience, characteristics, style, and also in the frequency in which they appear.
First lets consider what is "popular" literature. This type of reading material refers to widely-spread literature that reaches a myriad of audiences, and which deals with a diversity of topics that, like the name implies, are of common interest to the general public.
The purpose of popular literature is either to entertain, inform, or persuade a vast audience, and its authorship is usually delegated to a person hired by the organization which publishes the literature, namely, magazines, catalogs, pamphlets, or newspapers.
Popular literature follows its own style of writing, and it is often preferred to be in the form of a third person omniscient and objective narrative. When it comes to editorials or personal columns sometimes first person subjective narrative is more evident.
One more unique feature that differentiates popular from classic literature is the frequency with which it appears. Popular literature can appear in the form of periodicals, bi-weekly publications and other publications. However, the most salient difference is that popular literature reaches the mainstream reader with current topics.
Contrastingly, classical literature refers to well-established pieces of literature that have surpassed their time. It is reading material that continues to have relevance, instill interest, or inspire audiences, even years after its first year of publication.
Classic literature may actually start out as popular literature. This is the case with Dickens's Pickwick Papers which, later on, are published in book form, becoming a classic.
This type of literature also aims to either educate, entertain, or persuade. The authorship is delegated to an author who works independently and the specific book publishers edit and distribute the final publication.
Again, the main difference between both kinds of literature is their survival through time. Anything that persists time and continues to be relevant to society years after it is first published automatically obtains a historical importance. This importance is what, ultimately, deems a work as a "classic".