The growth of these sites has been phenomenal. Shortly after its purchase by Amazon in the spring of last year, Goodreads announced it had 20 million users. Whether this is an amelioration or a reflection of an increasingly atomized culture is a question that can be filed in the same drawer as Facebook friending or dating on Match.com. Certainly the range of collective knowledge in pools of this size is incontestable. But it derives from self-selecting volunteers whose authority is hard to gauge. And though the overall network is vast, recommendations are generally exchanged within tight circles of friends. This results in another typical Internet characteristic: the “mirroring” of existing tastes at the expense of discovering anything new.

THERE are many who will not mourn the displacement of literary culture’s traditional elite, dominated as it was by white, middle-aged men of comfortable means and conservative taste. Jeff Bezos, the C.E.O. of Amazon, aimed to exploit such disillusion with the old ways when announcing the launch of Kindle Direct. The self-publishing e-book program would, he claimed, produce “a more diverse book culture” with “no expert gatekeepers saying ‘sorry, that will never work.’ ” But to express discomfort at the attrition of expert opinion is not to defend the previous order’s prerogatives. Nor is it elitist to suggest that making the values and personnel of such professional hierarchies more representative is preferable to dispensing with them.

On the desolate beach that is the lot of the contemporary book reader, the footprints of one companion can still be found. They belong to the writer, who needs the reader not just to pay her or his wages but also to give meaning to their words. As John Cheever put it: “I can’t write without a reader. It’s precisely like a kiss — you can’t do it alone.”

The troubling thought occurs, however, that this last remaining cohabitant may also be about to depart the island. With falling advances, writing is evermore dominated by people who don’t need it to earn a living: Tenured academics and celebrities spring to mind. For these groups, burnishing a résumé or marketing a brand is often as important as satisfying the reader.

And then there are the hobbyists, those for whom writing is primarily an act of self-expression. This past November, National Novel Writing Month (Nanowrimo) encouraged more than 300,000 participants to produce a novel in 30 days. It would be churlish to gainsay the right of the legions taking up “noveling,” as Nanowrimo describes it, to exercise their creative selves. But such endeavors are not much helping readers. Indeed, to the extent that they expand the mind-boggling proliferation of new titles being published (more than 300,000 in 2012), they are adding to the problem.

Faced with a dizzying array of choices and receiving little by way of expert help in making selections, book buyers today are deciding to play it safe, opting to join either the ever-larger audiences for blockbusters or the minuscule readerships of a vast range of specialist titles. In this bifurcation, the mid-list, publishing’s experimental laboratory, is being abandoned.