If, Then is a masterpiece of a character-driven book. I read it eagerly and unflinchingly, and it epitomized for me all the best parts of strong, well-developed characters. I loved each of Day’s characters equally... and yet I never felt as though I had to race through one chapter to get to the next to see where a previous character was in his or her journey. They are each so fully realized and wonderfully fleshed out that it felt a bit like playing with a dollhouse, with each doll firmly in your line of sight ... I can assure you that every bit of the journey to the truth will be worth your while. Day is a remarkable and careful writer, and I cannot wait for scores of readers to find this book in whichever reality they inhabit.
If philosophy is a science, then Kate Hope Day’s first novel is science fiction ... But advance publicity compares If, Then to mainstream titles such as The Immortalists and Little Fires Everywhere. Certainly the depth and extent of the author’s character analysis feels literary. But that alone doesn’t disqualify its inclusion in the genre ... Small-scale seismic events occur before the mostly minute shifts in reality the book’s four narrators experience, yet the connection there comes across as almost coincidental. A hospitalized philosophy professor’s theory of parallel universes relates a little more clearly — not causally, but as a model of what’s happening.
Captivating ... Often, Day seamlessly slips readers in and out of realities with little warning, and the scenes in which characters observe and, at times, interact with, their alternate realities are intimate, eerie, and startling ... Effortlessly meshing the dreamlike and the realistic, Day’s well-crafted mix of literary and speculative fiction is an enthralling meditation on the interconnectedness of all things.
Day's first novel recalls the philosophical headiness of a TV show like Lost and remixes this sensibility with the chronological playfulness of Cloud Atlas or Atonement. But, until the story really takes off, the emotional stakes of the novel are low—and the prose feels flat and inert, almost like stage directions. There are more affecting moments in the second half of the book ... With all the atmospheric mist crowding out its emotional center, this book's heart is difficult to locate—but the occasional glimpses show promise ... A suburban drama built to leap from page to screen.