I am sure this happens to you all often. You get hooked on an author, eagerly awaiting their next release while voraciously re-reading their previous books to whet your appetite for the new installment.
You bring their newest shiny book home, perhaps you even call in sick from work to devour it. You crack it open and begin reading the first few pages with a joyous grin. Then, it starts. Your smile dims somewhat. This character would never do something like that. However, with high hopes, you read further. Perhaps there's a nifty twist to explain it. A few pages later, a perplexed frown mars your features. Either a crappy character or a cheesy plot device has entered the picture. And is that yet another typo?
You finish the book and close it, aching with disappointment. What happened? If this were anyone but your favorite author, you would have tossed the book aside by the second chapter. Nevertheless, meager hope shines in your breast. Maybe the author was having some personal issues. Maybe this bad book was needed to lead up to something awesome. But....you have a bad feeling. You wait for the next book, but not with half the excitement as before. You don't run to the closest bookstore to get it. Instead, you search for the best bargain, and even then part with your money grudgingly.
And your suspicions were confirmed. This one is even worse than the last. Still, you've invested a lot of time with this author and retain some loyalty. You wait until the next one is released in paperback...and again it was a waste of money. Better just get it at the library next time.
As a reader, I feel horribly betrayed when this happens.
As an author, I fall on my knees and pray, "Please don't let me end up like them!"
But really, what happened? I hear rumors sometimes that this or that author has literally gone insane. I read in the news that another had lost a close relative. Or perhaps it is as simple as not following Stephen King's credo to "write with the door closed" during the first draft. It is hard enough for an unpublished writer to refrain from talking about their project or even showing it to friends and family. I can't imagine what it's like for best-sellers whose work everyone and their cat is clamoring for. But like King says: "...if no one says to you, '....this is Wonderful!,' you are a lot less apt to slack off or to start concentrating on the wrong thing...being wonderful, for instance, instead of telling the goddam story."
Of course...there are a few out there that I am more in favor of the "gone insane" theory. :)