A young, bisexual love triangle is reaching domestic crisis in the grey cold of a Chicago Christmas Eve. After years of channeling his discontent into his writing, the cynical Xavier can no longer bear Hadley's repeated absences as she travels the world with her much older, richer husband; Hadley's fear of dividing herself between who she loves and who gives her freedom is becoming the constant target of Xavier's piercing wit; and lovable, pragmatic Jacob is growing tired of being the glue which holds their hectic triad together. As if this weren't enough, the throuple must juggle a lost pet, too much whiskey, and a futile effort to finish watching CASABLANCA while everything threatens to fall apart. In a shameless look at contradictions and comedy of millennial, poly love, The Book of Us invites us to consider what pieces we give to each other and which we selfishly insist are our own.