So, I’ve been thinking about this for a while now, which means hopefully it’ll be coherent, but I’m also sort of thinking as I type on this one.
I have certain authors that I enjoy and will buy their books whenever a new one comes out. I don’t read reviews, I don’t talk to other fans, I just buy the author’s latest book. And I’d hazard a guess that a lot of people are like that with authors they’ve already read and enjoyed.
Which means, unless you write something that is so atrocious that it inspires people to seek you out and tell you it sucked, that you’re not going to realize you’ve written a bad novel and possibly gone off the rails writing-wise for a few years and possibly for a few novels. At least not sales-wise.
Bear with me if the following examples are too vague. I try not to name names if I can avoid it.
Last year I read a book in paperback that was terrible. It was by an author I’d read previously and enjoyed, but this was such an awful book I swore I would never read another one by this author. Copyright on the book was 2010 and it looks like the author has since come out with at least one more book. I would say, based upon the fact that I read this author in paperback, that the author and publisher won’t see the effect of my disappointment for at least another book or two.
I’m the silent disappointed type. If I don’t like a book, I’m just done with the author. I have never gone on-line and posted a negative review of a book. (On this particular book I did tell a couple of friends who enjoy SFF to avoid it like the plague, but I’ve never felt such aversion to a book that I would purposefully go out and post a negative review.)
My mother, however, did exactly that with a book last year. (The author had already lost me years before.) She read a book that she hated so much it inspired her to start an Amazon review account just so she could explain to the world how bad the book was. This is a book that was on the top of the best seller lists. It made lots of money for the author and publisher. But if others reacted the way my mom did to that book, the next one will not sell well.
So, how do you know when you’ve lost a reader? If you’re an established author with an established fan base, I don’t think you can look at sales on your current novel. Your current novel sales are based on your established reputation and marketing efforts. And I’d hazard a guess that the more established you are, the longer it takes to see that you’ve lost your direction.
There’s one author whose writing I loved when I was a teenager, and the author came out with a new series that I tried to take an interest in and just couldn’t. I read the first two or three books in the series because I’d loved the author’s other books so much that I wanted to get into the new series, but I never could. Because this author had such a strong reputation and was constantly bringing in new readers through the other series, I suspect that the author never realized that the new series wasn’t up to the same standard as the prior one.
I don’t know. It’s something to think about. I’m not even close to that stage in my career yet, but I suspect this idea could be applied to all aspects of someone’s professional career. If you build up enough of a reputation, people will forgive you for mistakes and give you a chance to recover, but you can already be “failing” and not even know it.
Something to ponder…I may circle back to this one again.
M.H. Lee 
I’d guess that most authors in that position know that their new books aren’t as good as their early ones, but they don’t really care as long as the sales are good. That’s why I usually don’t read more than a book or two from any given author.
I like to think that they really do care what people think, but that sometimes they don’t understand what people liked about their writing. So they try to focus on improving in an area of their writing that wasn’t what drew people to them in the first place and end up losing readers as a result. That’s definitely what happened with the book my mom hated. The author focused on the details of the world they’d created at the expense of characters and story.
And I have to imagine that there’s an enormous amount of pressure on a popular author to continue to produce new material and sometimes when they succumb to that pressure they produce something that’s simply not up to their usual standard.
And when you’re that successful, there’s no incentive for anyone like an agent or editor to tell you that your newest book sucks. They should, but that’s not how things actually work. Pretty sure I saw some discussion of that on Miss Snark at some point.
And if you’re not reading more than one or two books by any given author, then I have to say that you’re missing out on a lot of great works. I can’t imagine only reading one or two books by Asimov or Marion Zimmer Bradley, for example.
I was a die-hard fan of an author for many years, purchasing every single book under the author’s main name and pen names. And then she changed her style. I hated her new book (new genre too!) so much that I haven’t purchased anything from her in five years. She recently released a new novel reminiscent of her old stuff, but I’m still hesitant to even try it. (You may know who I’m talking about now.)
It’s scary how many times that happens. I had one author whose first series I loved. Didn’t read the second one because it was sci-fi instead of fantasy and I wasn’t sure I wanted to go there. Read a stand-alone book by that author after the sci-fi series that was awful. AWFUL. Finally went back and tried the author’s next series because it was the only thing interesting at the library that day and it turned out to be pretty good and when I went back to the sci-fi series it was decent enough that I didn’t regret reading it. But he came close to losing me forever with that stand-alone…
Maybe you can check out the newest book by the author from the library and see if she’s finally got her mojo back? Then at least you’re not out the money if it sucks…It’s so hard to find good authors that I want to give them chances, but there’s nothing worse than suffering through a miserably bad book.