The Hoover Dam on the border of Nevada and Arizona is 726 feet high and 1,244 feet across. But another dam in Michigan's Upper Peninsula is more impressive. Made of wood, mud, rocks and whatever other materials were available, this dam is six feet high and more than 260 feet long. And it's more impressive because the builders had no printed plans, heavy equipment or opposable thumbs. They lacked hard hats but had hard teeth. To accomplish the feat, they also relied on their feet, the rear two of which are webbed. And their determined brains come hardwired for aquatic architecture. You probably don't need to be slapped with its broad, flat tail to have by now sussed out that we're talking about Castor canadensis, aka the North American beaver.

The Michigan dam description comes from environmental journalist Ben Goldfarb's engrossing and elegantly written new book Eager: The Surprising, Secret Life of Beavers and Why They Matter. People have used them for food, currency and hat-making material—the human desire for warm and stylish chapeaus almost wiped beavers out. But their population is rebounding as we recognize that beavers can restore ecosystems. Goldfarb quotes one scientist's wise counsel: “Let the rodent do the work.”

Before the near clear-cutting of the species, beavers engineered great swaths of North America: a study found that prior to the arrival of undocumented immigrants from Europe, the continent was the site of between 15 million and 250 million beaver ponds.

Goldfarb guesstimates, using midrange numbers and pond sizes, that beavers submerged some 234,000 square miles. Real estate busts don't leave that much property underwater. A lot of that saturated, wet, moist or merely damp land dried up after “trappers de-beavered North America,” as Goldfarb puts it, which “left behind some of the finest soil a farmer could till.” The bountiful agricultural output of the young U.S. and Canada rested on the shoulders of rodent giants.

The ghosts of beavers past still haunt New York City, where Scientific American is based. Our official city seal features two beavers. The walls of the Astor Place subway station include bas-relief beavers gnawing on terra-cotta tree trunks. (John Jacob Astor made his financial killing on beaver furs.) And a few short blocks north of our current offices, you can stroll down Beaver Street. Or flee down it, depending on the situation. What I didn't know until I read Goldfarb's book was that when the Dutch bought Manhattan from the Lenape in 1626, the island “was little more than a pot-sweetener: The real prizes were the 7,246 beaver skins that sailed to Europe.” I now choose to think that self-portraits by the hatted Vermeer and Rembrandt include New York City beavers on the masters' heads.

Within its wide scope, Eager includes other nuggets sure to make you the most fascinating conversationalist at your next party. Which, if it's in Sweden, could include the drink brand BVR HJT (pronounced bäverhojt or called “beaver shout”). It's schnapps flavored with beaver musk. One blogger wrote that the drink wasn't strong, but the smell that soon seeped from her skin was.

Nugget: Beavers engage in “caecotrophy, eating their own pudding-like excretions to extract every last iota of nutrition.” Goldfarb notes that after the second go-through, what comes out of the beaver is “nearly sawdust.” Perhaps an enterprising ecology Ph.D. candidate can one day quantify “nearly.”

Nugget: Beavers have a second set of lips behind their teeth, thereby “permitting them to chew and drag wood without drowning.” Once exposed to that information, the reader will immediately recognize the necessity of that evolutionary innovation. The reader could also be creeped out.

Nugget: In 2016 canoeists noticed a prosthetic leg, presumably load-bearing, in a beaver dam in Wisconsin. They plucked it out, found the owner via a Craigslist ad and returned it. He'd lost it a few weeks earlier when his canoe tipped over. As he told a local news outlet, “I wasn't overly worried about it, because I use my older model for fishing and hunting.... It wasn't my everyday leg.” Seems he took the whole episode in stride.