We would hope that as in the old adage "you can't keep a good man (or woman) down" a book of sufficient excellence will rise to the top, clawing its way there by merit, lifted by word of mouth.
Look at it another way though. We've all tried and failed to light a fire in our lives. There's no argument that fire is a supremely successful way of generating heat through oxidation ... and matches are perfectly sensible ways to initiate one ... and wood burns...
how often have we just ended up with burnt fingers, blackened kindling, and rapidly dissipating smoke?
If your book is not the sort that will get the typical reader to demand the next person picks it up then you are trying to light a fire in a swamp. In the rain.
If your book is The Name of the Wind then you are trying to light a fire in a tinder-dry forest.
If you have a big publisher behind you that's rather like having a friend with a ten gallon drum of gasoline to help you start the fire. Even then, if the book you're selling really isn't that good (or commercial if you prefer) the fire will peter out after carbonizing a few acres (selling ten thousand books), but nobody will be able to say it didn't have every opportunity to spread.
(Note, that not everyone published by a big 5 publisher has that publisher 'behind them'. Plenty of those releases are left to fend largely for themselves.)
A good small publisher could be likened to a friend with some firelighters, scrunched up, newspapers, and a cigarette lighter. A bad one is more like an acquaintance who grudgingly hands over one match.
When you're self-published you have a stick. Not a matchstick. Your job is to break it in half and rub the two pieces together and set the world alight.
Josiah Bancroft has been standing in a tinder-dry forest for three years waving his stick around gamely. Lightning did not strike. There was no fire.
It would be unfair to say that Josiah is bad at self-promotion. He's done more than I ever could just by going to conventions and hand-selling his book. I lack almost every one of the necessary skills and personality traits to do that. I'd probably be asked to leave.
I'm not sure what else he could have done if I'm honest. There's no secret path to self-published success. I think the main 'trick' he missed out on is becoming a bigger part of the self-published community itself. If you strike the right notes on the right self-publisher forums then your fellow writers become the gasoline and can give you a decent start.
Anyway, after 3 years Senlin Ascends had fewer than 50 ratings on Goodreads.
In April Senlin Ascends was entered for the Self-Published Fantasy Blog-Off, 2016. In June it got a blisteringly good review from Pornokitsch. In August I read first Senlin Ascends, then the follow-up Arm of the Sphinx, and reviewed them on Goodreads and raved about them in general. In September I somehow got Goodreads' global #1 best reviewer (with 50,000+ followers) to read Senlin, and she loved it.
Here's how these events impacted the book's "to read" and "ratings" stats on Goodreads (click for detail).
Those "to reads" won't all translate into purchases, but some of them will, and each read is another spark that could push the embers into the full-fledged inferno the book deserves.
The only note of caution here is that this book isn't the kind of work that I (perhaps wrongly) associate with a viral self-pub wildfire. For example it's nothing like Ryan's excellent Blood Song. It is not a high octane kill-fest, there is no cool sword swinging hero. It is (at the risk of sounding pompous) a book for the thoughtful, the clever, and the experienced. It is perhaps a book most suited to traditional publication. But I'm hoping that the push it's been given will let it find its way regardless.
Returning to the main point. Self-publishing is HARD. Excellence by no means guarantees success. And there may be dozens of utterly brilliant books out there, the authors busy rubbing those two sticks together, and doomed never to get a flame.
It's clear that the importance of the super-fan, the reader who goes out and actively evangelizes on behalf of a book that has really meant something to them, cannot be over-estimated. Especially when an author is starting off. You might ask, what can one person do? But a passionate independent voice can make a huge difference. If you love a book, talk about it. Talk about it to friends and family in the real world, talk about it on social media, talk about it on forums. It makes a difference. It can make *all* the difference. You can be the spark.
In any event, all of this makes me very glad to have set the ball rolling on the SPFBO!