To signal certain books are of especially high quality, self-publishing companies must handle two broad problems.
First, their high quality books must overcome the same stigma self-published authors must: if a book “couldn’t” get a “real” publishing deal, what’s the matter with it? Certainly this prejudice has been abating of late, and in fact, many authors now don’t even bother with the Traditional Publishing Path in the first place, so it’s not always a question of ability but desire to go the traditional route. Still, if a self-publishing company vouches for a book, it can ill afford backing a bomb, or even a mediocre book: That would simply reinforce the image of self-published books as inferior, as books that couldn’t make it the “real” way, which in turn would hobble the publisher’s ability to make money actually selling the books they publish.
In other words, if a publisher gets behind a book, it has to make absolutely sure it really is that good: a publisher’s not only protecting their brand but the business model of a whole class of publishing.
Second, how can a self-publisher, which by definition publishes whatever it gets paid to publish (with some exceptions)—including books that are not meant to be sold, or that are poorly written and rushed into print without so much as a proofread—legitimately signal that particular books are in a class above everything else it publishes?
A publisher might choose to have a unique imprint for these special books, such as Little, Brown and Company is for Hachette. But doing so would imply that everything else it publishes isn’t up to a certain level of quality. Not something most would be keen to do: few authors wish to be stuck with an imprint known for inferior quality books and might publish elsewhere, just as many readers might turn up their noses at books from such an imprint. Further, that would sever the best books from their main brand, which would dilute the perception of the overall rising quality of self-published books by cordoning off the best as exceptions and leaving the rest to wallow in old biases, justified or not.
So without denigrating everything else it publishes, how does a self-publisher send a clear signal that booksellers, critics, bloggers and readers would recognize as an assurance of superior quality?