Well, Miss Snark might have a better or different view (regarding character driven novels) but...in my experience, I had two previously agented, submitted novels that made it to the marketing committee level but didn't sell. And both were labeled somewhat "quiet" novels - the books were about relationships, women who grow into their own - i.e., in my own view, "character-driven" in that events didn't really drive the narrative; the characters' growth and development and reflections did. In retrospect, I'm forced to admit that there was very little plot, to speak of. And I have no better proof of this in the fact that really, I'd be hard pressed to write a compelling hook for either, beyond "Well, these two girls are friends and then they grow up and their friendship changes and then some stuff happens, but they remain friends in the end."
Um, not very compelling.
It wasn't until I wrote Confessions of Super Mom that I really understood that there have to be external events driving the narrative, events that FORCE the character to change (or not; that can be compelling, too). And these events have to be carefully constructed to have a beginning, middle, end, as well as high stakes involved - in other words, you know: A Plot. And once I did this, I was able to finally come up with the hook, the short description of the book I mentioned above. (And also - I was finally able to sell a darned book.) Characterization is still important, of course, and that's where I always start. But there has to be a reason for the reader to keep turning those pages, wanting to know what happens next, and I think - at least in my case - it's much easier to do that when you have A Plot.
That says it pretty darn well.