Finishing the manuscript for a book is usually the consummation of years of work, and when writers emerge on the other side, they often try to do something appropriately celebratory. For his new book, “Entangled Life: How Fungi Make Our Worlds, Change Our Minds, and Shape Our Futures,” the young fungal biologist Merlin Sheldrake decided on a ritual I had never heard of, much less fathomed. He dampened a copy of the book and seeded it with spores, eating the oyster mushrooms that sprouted from its pages. Taking another copy, he tore up the pages, mashed them up to release their sugars and fermented the solution into beer. Forget the trite literary pleasures of a gourmet meal or a champagne toast: Here is an author who marked the completion of his book by ingesting it.It’s a fittingly eccentric end for “Entangled Life,” Sheldrake’s ebullient and ambitious exploration of a subject that surrounds us yet too few of us think about. Plants get so much human attention, but Sheldrake wants to direct our gaze at fungi, without which so many of the plants that we take for granted wouldn’t exist. If you think about fungi at all, you might conjure an image of a mushroom, sprouting from a tree stump or ready to be eaten from a plate. (Sheldrake’s first name — Merlin — helpfully makes me think of a wizard and his enchanted toadstool.) But mushrooms are just the minuscule flowering tip of the vast fungal world. The largest recorded fungal network is in Oregon, a network — or mycelium — that covers four square miles and is thousands of years old.What’s more, fungi are not only everywhere; they are doing things. Though they often get lumped in with the plants that used fungi as root systems for tens of millions of years before the plants evolved their own, Sheldrake says that fungi are more closely related to animals. When thinking of plants and the fungal networks that sustain them, we too easily fall back on a “plant-centrism” that makes us “fungus-blind.”Our blindness can make us miss out on some extraordinary phenomena. Fungi can distribute nutrients and even information across plants. For instance: A plant subject to an aphid attack emits a “chemical shriek” that can be “heard” by other plants in the fungal network, allowing the linked plants to prepare themselves by emitting a chemical that will summon wasps, which will then eat the aphids. Even if the sender plant gains little or nothing by alerting its plant neighbors after the aphids arrive, the fungal network benefits by keeping the healthy plants alive.But mycelial networks — what some mycologists call “wood wide webs” — can also amplify fungal, plant and bacterial interactions with more ambiguous results. A network can transmit poisons and viruses, allowing plants a speedy route to kill other plants nearby.The biologist Merlin Sheldrake, whose new book is “Entangled Life: How Fungi Make Our Worlds, Change Our Minds, and Shape Our Futures.”Credit...Hanna-Katrina JedroszSheldrake’s book is full of striking examples like these, prying open our cramped perspectives. He offers motley quotations, all of them enigmatic yet pertinent, from figures as varied as Tom Waits and the French feminist Hélène Cixous. An early chapter on truffle hunting begins with a line from Prince before delving into the mysterious world of fungal sex. Examining a plant’s roots under a microscope affords him a chance to glimpse the plant and the fungus grasping each other in an intimate embrace. “This wasn’t sex,” he writes; no genetic information had been pooled. “But it was sexy.”True, rank anthropomorphism presents certain dangers; if we abandon plant-centrism in favor of projecting human qualities onto fungi, Sheldrake concedes, we risk failing to understand an organism on its own terms. But there is some value in recognizing that fungi can be unpredictable, responsive and excitable. He mentions that the Potawatomi word for “hill” is a verb: “Hills are always in the process of hilling, they are actively being hills.” Later, in an unexpectedly enthralling discussion of lichens — composed of a symbiotic relationship between an alga and a fungus — he explains how lichens leach minerals from nonliving rocks and pass them on to the metabolic cycles of the living. Lichens, in other words, “never stop lichenizing; they are verbs as well as nouns.”Enterprising researchers are finding ways to put fungi to all kinds of uses. There are the basic fungal tasks of supplying nutrients to plants, helping them grow and changing, say, the sweetness of a strawberry. But could they also help us clean up the horrible mess we’ve made of the planet? Fungi can be trained to eat cigarette butts, used diapers, oil spills and even radiation. A budding field of mycofabrication has developed imitation leathers and building materials out of fungi. Sheldrake visits a factory that turns fungal networks into furniture — footstools instead of toadstools.But to fixate mainly on their practical potential is, in some ways, to miss the bigger point. Sheldrake says that paying attention to fungi can transform our fundamental understanding of the world. Mycelial networks are decentralized organisms, whose “coordination takes place both everywhere at once and nowhere in particular.” They eat by putting their bodies into food. Tiny fungal tips called hyphae can exert enough pressure to penetrate Kevlar. A mushroom that sprouts from the ground after a rainstorm can crunch its way through an asphalt road. “If I think about mycelial growth for more than a minute,” Sheldrake writes, “my mind starts to stretch.”He describes getting a little help from fungal hallucinogens like LSD and psilocybin, making a mind-bending analogy to so-called zombie fungi that commandeer the bodies of their insect hosts. One fungus propagates itself by infecting cicadas, keeping them alive while causing their rear ends to disintegrate and discharge spores, turning them into “flying saltshakers of death.”Fungal psychedelics are usually more benign to their human hosts, Sheldrake says, but are similarly powerful. They encourage humans to cultivate them, spreading their spores along with the word. They can blur the boundaries of the self, giving people the feeling of merging with something greater, expanding their universe of possibilities. Instead of staying trapped in our individual “I,” we might start to think of ourselves as part of a dynamic network, embedded in a filigree of relationships.Within 24 hours of finishing “Entangled Life” I had ordered an oyster mushroom-growing kit. I started scrutinizing the lichens that hug the damp concrete in the yard. This book may not be a psychedelic — and unlike Sheldrake, I haven’t dared to consume my copy (yet) — but reading it left me not just moved but altered, eager to disseminate its message of what fungi can do.