Some years ago, a friend found my doppelganger. This person’s photo was posted on a wall in a cafe somewhere in Tokyo. My friend snapped a picture and sent it to me. The similarities were remarkable—this guy had the same head shape, the same style of glasses, the same facial features, and even the same general vibe. Beside him was a woman who, of course, looked unfamiliar to me. It was strange to see someone who looked so much like me sharing a moment with someone I’d never met. It was good for a couple of laughs.

I could not help but think for a split second: this person is living an alternate life that I could have had. He knew different people and had different experiences. Had I taken a different path and made different decisions, could I have ended up as that guy in Japan?

Isabel J. Kim takes this idea and runs off with it in a wildly creative way with her debut novel. Sublimation is a speculative peek behind the curtain of the ever-alluring road not taken. It’s also a science fiction story that explores a wide range of ideas: the multifaceted nature of humans, the uncertainties of immigration, and how disruptive tech can change lives in a big way.

The central premise of Sublimation is that people can literally split into two: the in-universe term for it is instantiation. Each instance is essentially a fork of the original: they are the same person up until the moment of instantiation, but thereafter free to live their own separate life. What makes this idea especially interesting is that technology has nothing to do with instantiation. Instead, it’s part of the natural history of Sublimation’s world. When faced with a seemingly permanent choice, like immigrating to a different country, a human’s opposing desires can cause them to instantiate. When this happens, one instance goes off to a new life, and the other stays behind amidst the comfort of familiarity.

When instances come into physical contact, a reintegration happens: both entities meld back into a single person carrying the personalities and memories of both lives. In the 21st century, a wearable device called a MERGEBREAK exists to prevent accidental reintegrations.

The novel carefully builds on this instancing phenomenon, sharing sidebars of analyses of how instancing has influenced alternate versions of such tales as Adam and Eve in the Garden of Eden, Homer’s Odyssey, and the Korean folk song Arirang. Marco Polo, so sure of what he wanted out of his adventures, famously did not instantiate in Sublimation’s version of history. The world is the same as ours in every other aspect, but the degree of detail in which Isabel Kim has explored the probable effects of instantiation is astonishing.

Perhaps the novel’s most fascinating act of worldbuilding is how it re-imagines the United States. America, a nation built by immigrants, is a nation of instances. In Sublimation’s world, most first-generation immigrants in America have an instance living their own life back in the old country.

The novel begins with a very personal situation: Kang Soyoung, who has lived in Korea her whole life, has just lost her Harabeoji—her grandfather. She also happens to have an instance who has lived in America since they were eleven, and Soyoung invites her instance, Rose, to come home for the funeral.

Rose and Soyoung have had no contact since their separation. Rose is happy with her life in New York. Soyoung, however, wants to reintegrate.

This initial meeting kicks off a series of events that take them on a strange adventure of self-examination with life-changing and eventually world-changing implications. Sublimation ends where most dystopian science fiction stories would begin: with humans discovering a way to harness and exploit a force of nature.

Sublimation isn’t a dystopian story, though. Like its instances, it seems like it wants to be many different things. It’s a family drama. It’s a tech thriller. It’s a love story featuring the strangest love triangle imaginable. Like with all good stories, its heart lies in its characters. Rose and Soyoung are very flawed humans with many weaknesses and hang-ups, but it’s easy to root for them because they are written so sympathetically.

It’s also not beneath Sublimation to employ a few eyebrow-raising coincidences and leaps of logic, particularly in how some characters happen to be in the exact oddly specific circumstance to properly move the plot along. However, the story is stronger for it in the long run: the final third of the novel barrels along relentlessly, frantically weaving perspectives and plot threads together towards a tantalizingly provocative conclusion.

Sublimation brings the delight of seeing your doppelganger’s photo pinned to the wall of a Tokyo cafe, and quadruples down on it by dropping an entire engrossing and thought-provoking story to go with it. Like the alternate lives it imagines, it’s difficult to stop thinking about what might have been and what could be long after it concludes.