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In "Serendipity," one of the short but potent essays in this essential new book, Sven Birkerts takes the measure of Netflix, Pandora and other ubiquitous Web-based entertainment services. He's not unimpressed with their if-you-liked-this-then-try-that recommendations, but he's skeptical, too: What is all this intuitive technology doing to our brains? Is it subtly modifying "our malleable neural psyches"?

These are legitimate worries, and yet Birkerts knows that in our screen-worshiping era, they don't appear to be widely shared. As he puts it, "I once again feel as if I'm setting myself up against an almost universal enthusiasm."

He must be used to it by now.

Two decades after the publication of "The Gutenberg Elegies," his against-the-grain book about the potential downsides of the nascent World Wide Web, Birkerts is back to take another swing at our age of 24/7 interconnectedness.

A professor, editor and prolific writer in Massachusetts, Birkerts has published several titles in the intervening period. But as he makes clear in "Changing the Subject: Art and Attention in the Internet Age," the Internet's stealthy knack for insinuating itself into every aspect of our lives is his perennial fixation.

"It has to be examined by all of us who are implicated — not just in terms of the cultural marketplace or of the altered behaviors it creates," he writes in an essay about the meaning of the word "Luddite," "but also psychologically and, if I can bring in these old-school words, metaphysically and spiritually."

Birkerts comes at this timeliest of topics from a number of different angles. He's not a technophobe — he just thinks we'd be better off if we were a little more judicious with our electronic devices.

In an essay titled "The Still Point," he reflects on the 2013 death of his friend Seamus Heaney, the revered poet, and how mastering a language, or appreciating prose, verse or visual art, demands a degree of intense mental energy. Heaney, he writes, "knew that imagination, its requirement of attention, cannot be sustained where the signals flash too distractingly."

In "You Are What You Click," Birkerts notes the effect that technology seems to have had on civic engagement and debate, perhaps contributing to "a political discourse that has become jittery and insubstantial, in a public life where values and seriousness seem to have dissipated into thin air."

And in "On or About," the book's longest and most idea-laden essay, he frets that his devices have alienating properties — "Technology has interposed a finely woven scrim of signals and distractions between me and my physically immediate reality" — and endorses device-free timeouts devoted to "great art," which "arms us, if only for a time, against the depletion that threatens on every front."

Even those of us who'd never leave home without a smartphone in hand have to concede that Birkerts raises some significant concerns. The delivery of information has changed tremendously since the 1990s, and it seems foolish to ignore what this epochal shift might mean to our cultural lives, our relationships, our attention spans and our democracy. Birkerts says he's "not ready to assent" to the total technological takeover of contemporary life, and in "Changing the Subject" he makes an inspired argument that his is a campaign worth supporting.

Kevin Canfield is a writer and critic in New York City.