In October of 1994, Wired magazine ran a feature about a new Californian subculture, cheerfully titled “MEET THE EXTROPIANS.” Extropianism, the article enthused, was a philosophy of transcendence. With technology and the right attitude—aggressive individualism, cool rationalism, and other vaguely libertarian leanings—followers of the movement would “become more than human.” They would become transhuman, possessing “drastically augmented intellects, memories, and physical powers,” or maybe even post human. They envisioned a future in which human brains would be downloaded and preserved for posterity. So, too, would the human body, through cryogenics.

TO BE A MACHINE by Mark O’Connell Doubleday, 256 pp., $26.95

These transcendental technologists took the word extropy to mean the opposite of entropy, the process by which all things eventually decay, and they imagined a way of life to match. The Extropians invented an exuberant handshake to greet each other, and referred to themselves as VEPs, or Very Extropian Persons. When they gathered, they called it an “Extropaganza.” An article from Extropy magazine, published in the mid-Nineties, laid out their vision for existence. “You can be anything you like,” Extropy promised. “You can be big or small; you can be lighter than air, and fly; you can teleport and walk through walls. You can be a lion or an antelope, a frog or a fly, a tree, a pool, the coat of paint on a ceiling.” The Extropy Institute, which shuttered in 2006, defined its work as “a symbol for continued progress.”

In their early days, the Extropians looked quaint enough: a group of technophilic counterculturists clustered in a hot tub. But they helped set the stage for a sector of the tech industry that has, of late, been flooded with money from philanthropists and venture capitalists alike. Life extension, artificial intelligence, robotics, and other posthuman ambitions are still very much a part of the techno-utopian agenda, in a way that’s more mainstream than ever. Venture capitalist Peter Thiel is looking into blood transfusions as an anti-aging treatment. (“PETER THIEL IS VERY, VERY INTERESTED IN YOUNG PEOPLE’S BLOOD,” Inc. reported last summer.) Google co-founder Larry Page has invested $750 million in Calico, a laboratory for anti-aging technologies. And in 2012, Google appointed Ray Kurzweil, a futurist who believes artificial intelligence will soon allow humans to transcend biology, as an engineering director.

It’s easy to take these ambitions more seriously than those of the Extropians. It’s harder to know where they will lead us. In To Be a Machine, the Dublin-based writer Mark O’Connell infiltrates groups of transhumanists with the aim of discovering how they think and live. A literary critic for Slate and a former academic, O’Connell is less interested in evaluating technology than in the people who make it and its philosophical implications. As he places the quest for immortality under the microscope, he follows the individuals—tech visionaries, billionaires, and futurists—who are trying to eradicate, or dramatically postpone, death. “I wanted to know,” he writes, “what it might be like to have faith in technology sufficient to allow a belief in the prospect of your own immortality.”

This might be another way of saying that the idea of living forever is as influential as the actual possibility of living forever. Immortality is a long shot. But why is it such big business now?