This was a comment originally made by me on the Amazon Kindle boards in response to many readers complaining about the low standards. Not just with plot and style, but typos, grammatical errors, etc.
However, I've found myself biting my tongue slightly on this issue, having had problems on one book with OCR sampling. If you want to see a book series that has suffered the same nightmare, check out the reviews on George R. R Martin's Game of Thrones. LOL. More on that later, but here for now are my original comments.
It's very true that sampling or trying to find quality books amongst such a volume becomes a game of diminishing returns.
And I suppose pretty much the same process has in fact already been experienced within trad publishing itself. I recall years ago that every major publisher had staff on hand to read the incoming slush pile of daily manuscripts.
Such was the incoming volume with such a low degree of even passable grade manuscripts that it didn't even pay their staff to keep the slush piles open. So one by one they shut their doors and passed that (often thankless) task to agents.
I recall an interview with a US editor talking about his first day as a novice assistant at a big publishers, and he was given the task of handling the slush pile. He was told to open the packages, slip a standard rejection slip in each, and put them back in their pre-paid envelopes. He asked, 'What - don't I read them first?'
'God, no!' came the answer. 'We need your help with books that we ARE going to publish.' He was talking as an editor at McAdam Cage - who did in fact at that time actually trouble to read what came in (thus the boast about the contrast to the big bad publisher from his novice days).
Agents too often get fed up with the deluge, and the only way to get through it is sample just the first few pages, or at most the first chapter. From that they pretty well know whether the person can write or not. If it goes beyond that (and 98/99 of a 100 don't), then they're in with a chance.
Shift that slush pile straight to readers, and it's hardly surprising that their attitudes are going to harden in the same way. Who the hell has got time to sift through 100 sample books in the hope of finding one or two gems? The publishers got fed up with doing it long ago.
Even picking solely amongst trad published books, there's a high quota of mediocre or lack-lustre books; by the time factors of genre, taste and style are taken into account, you might be lucky to find one good book in ten. Truly GREAT books are even rarer -- so it doesn't take much to work out the odds without all that gatekeeping of agents, editors and copy-editors in place.
And the reason they're all there - even when they have finally sifted down to the books they feel are worthy to publish or will work commercially - is that they know that unless they hone and polish that book to shine as best it can, they'll get panned by critics and readers alike.
So, without those people to hand, then it befalls every Indie writer to do the best job they can with self-editing and polishing so as not to run that risk of getting panned. Or, as has been covered here ad nauseum - not simply transfer those vast slush piles from publishers desks to readers, so that readers end up closing their doors one by one, just as publishers have done in the past.