Novels are often described as "plot-based," or "character-based," and there are important differences. Of course, all novels (or, at least, all but the most experimental or misguided) have both plot and characters, but often the balance is what matters. So-called "mainstream" novels, meant to appeal to a wide audience, tend to be plot-driven. So-called "literary" novels, meant to find an audience interested in other things than plot, are often character-driven.
The Harry Potter novels are a good example of plot-driven novels: lots of things happen, lots of fascinating details are described, and the main characters are in for a bumpy ride. J.K. Rowling typically spends the first half of her novels setting up an exciting, action-packed second half. But, though the personalities and quirks of the main characters are important, we're more interested in what happens to them than in who they are.
E. Annie Proulx's novel The Shipping News, published in the 1990s, is a good example of a best-selling literary novel, and one that is essentially character-driven. The main character, a sad sack loser named Quoyle, takes a last-ditch job in an out-of-the-way place, and his development from a schlub into a competent and even heroic protagonist is what gives the story much of its appeal. What happens to Quoyle is important, but we're more interested in who he is and how he must change.
A key to writing a good novel is understanding what you're after, and getting the balance right. A thriller that spends too much time plumbing the psychological depths of its main character is likely to frustrate readers. And too much wham-bang plotting can harm a novel whose main attraction is the sensitive portrayal of its main characters.
Do you know where your novel fits on the spectrum? Is the balance right? Often, when you're in the middle of writing your book, that sort of perspective is hard to come by. That's where someone like the Book Doc can help.