The etymology for the prefix dates back to use of Metaphysics as the title of the treatise by Aristotle that came after his works on physics in the traditional ordering of his books.
The modern, inferred meaning of a higher-order, self-referential consideration of the nature of an activity—rather than actual, first-level participation in the activity—has led to many neologisms such as Meta-Wiki.
On-topic discussion of a novel, rather than meta-discussion, would include such things as the consideration of a particular character, examination of incidents in the plot, or exploration of the general themes of the book.
For instance, writing or talking about the unnamed governess in Henry James' The Turn of the Screw would constitute on-topic, first-level discussion.
Tactful consideration of personality issues with some contributors as revealed in a discussion may lead to better insight and calmer exploration of the primary topic of the conversation.