Why is it that certain novels are given the added designator “a novel” and other novels are not?  Is it perhaps because there may already be a book with a similar/same title, in which case the suffix descriptor is useful/needed?

Always wondered about that.  I bet it is just something the author (or publisher) decices to throw down long after the book is written, before final publication, and on a whim or as a dare.

Thought?  Explanations?

thanks