In a way it’s fitting to review John Park’s Janus in January, a month that often finds us looking both forward and backward like the Roman god after which it was named. That same duality forms the tension at the heart of Park’s novel.

Janus is a world on the other side of “the Knot” from Earth. As one character puts it, “It’s the same sort of place as ours, but it’s not ours. Or if it’s ours, it’s not ours when we left it.” Travelling through the Knot has unfortunate side effects, most notably the amnesia that affects nearly a third of the colonists. One such member of the “unlucky thirty percent” arrives on the same day that someone distributes mysterious leaflets in the cafeteria alleging that dangerous criminals and psychopaths have been sent to Janus to live among the colonists.

It’s to Park’s credit that he allows the reader to make the connections between these facts, and that the confirmation that comes about halfway through isn’t treated as a world-shattering revelation. The story relies less on surprising twists and is more concerned with the idea of starting a new life in a strange new world, and whether it is possible to look forward at all when one doesn’t have the option to look back. The central conceit of memory loss and memory recovery is perhaps especially well suited to our neuroscience-obsessed times, but memory has been closely tied to our sense of identity. If you don’t know the choices that got you where you are, what guides your decisions about what to do next? The colonists without a past must wonder whether there was a dream they wanted to pursue at the new frontier, or were they running away from something more than they were running to anything in particular?

Memory or no, each new colonist is assigned a role in the community, and the rootless among them are left to create themselves anew based only on their new responsibilities and scant clues about their histories. Jon Grebbel, the lone arrival at the beginning of the novel, soon meets Elinda Michaels, an amnesiac for whom the standard memory therapies have had no effect. Grebbel bears mysterious scars on his arm, a legacy from his past self that he is driven to understand. Elinda tries to focus on the present, but the glimpses she sees of her former life prevent her from committing to it fully. As their memories return, each character is forced to find his or her own equilibrium among the masks they have worn on Janus and on Earth, and whatever authentic self may lie underneath. And over time, sinister events are uncovered in both in their Earthbound pasts and on Janus.

The book falters a bit in its third act: The restoration of the characters’ memories doesn’t quite have the impact it feels it should have. Their backstories play more like plot devices than foundational parts of the characters — rather than making them whole, the past becomes another thing for them to feel ambivalent about, which is thematically appropriate but not entirely satisfying. As the pace quickens toward the novel’s climax, Grebbel hatches an intricate plan whose goals are unclear and there is an unnecessary villain monologue that undercuts the subtlety with which the revelations have unfolded up until that moment.

Ultimately, this is perhaps a book that is a bit too relentlessly about what it’s about. Everything that happens is perfectly on-theme. The setting of Janus is tailor-made as a stage for these events to play themselves out. The worldbuilding is not overly detailed, but the details feel right, and a well-rounded cast of secondary characters helps to shed light on different facets of the problems that face the colony.

I confess to being a sucker for stories about identity, self-invention and the slipperiness of memory, so I enjoyed the existential drama of Janus despite its flaws. The premise is one that lends itself more easily to questions than answers, and I found the early part of the book that lays out those questions more compelling than the latter part when it flips into resolution mode. But these are ambitious questions for a first novel to tackle, and if you are intrigued by the prospect of exploring them too, then the world on the other side of the Knot is well worth a visit.