The Impossible Lives of Greta Wells features time traveling, but sci-fi is secondary. The focus of Andrew Sean Greer’s fourth novel is nothing less than love: a force known for its power to transport. Greta Wells lives at Patchin Place in Manhattan’s West Village in 1985. Simultaneous losses—the death of her twin brother, Felix, from AIDS, and the departure of her long-term lover Nathan—lead Greta to a dark night of the soul.

A doctor prescribes a series of electroconvulsive therapies, and the morning after the first great shock she awakens to many more: The buildings outside her window have changed, as have her furniture and clothing. Nathan is her husband away at war. Felix is alive. It’s 1918.

Greta takes it better than most might. “You make a wish, and another world is formed in which that wish comes true, though you may never see it. And in those other worlds, the places you love are there, the people you love are there,” Greer writes. “Perhaps in one of them, all rights are wronged and life is as you wish it. So what if you found the door? And what if you had the key? Because everyone knows this: That the impossible happens once to each of us.”

The second procedure, more primitive than its ‘80s iteration, shocks Greta into 1941: another Nathan, another Felix, another war fomenting. Round and round she goes, cycling among three lives with no end in close reach: She’s scheduled for 25 treatments over 12 weeks. The gambit allows Greer to explore the implications of time on people and place. Greta narrates, but both twins have much to gain from society’s evolution: In 1918, Greta can’t legally vote; in 1941, Felix is forced into a sham marriage with a senator’s daughter.

Their marginalization fuels rich reflection throughout—a component added when the book was already underway. When Greer began writing, the protagonist was a man. “Straight men often take the world just as it is because it’s made for them, so there’s often not a lot of conflict except: What do I want to do now?” Greer says. “For Greta and for Felix, as a gay man, the question was, ‘How do I get what I want given what I’m allowed to do?’” he explains.

To bring each era to life, Greer spent a fellowship at the New York Public Library poring over primary sources. “A lot of my research was not to read history books, but to read the newspaper and all kinds of ephemera. That’s my technique these days and what I recommend to my students: Find things you can’t Google,” he says.

For example: “Bloomingdale’s in 1918 was full of postwar bounty, and the windows cried: PARIS SAYS FLOWERS FOR HAPPINESS! Girls in fresh white blouses smiled above sparkling counters, each with a penny in hand in case they found a thief among the browsing women; they were to tap on the glass to summon the store detective,” he writes. Pamphlets, maps, advertisements, including Katz’s Delicatessen's famous “Send a Salami to Your Boy in the Army,” and a Navy guide for sailors on shore leave informed authentic flourishes in every period Greer writes about.

Greer wields his knowledge well, coercing the reader to inhabit successive worlds as Greta does. “I hope readers can have that magical experience,” he says, “like when you put a book down when you’re a kid and, for a little while, you think a dragon’s in the closet—that they can be persuaded for a little while that the book is true.”

Megan Labrise is a freelance writer and columnist based in New York. Follow her on Twitter @mlabrise.