The book alternates between Heather's and her mother's experiences of succumbing to an invisible illness that manifests itself in myriad symptoms of distress and confusion. Though Spargo-Ryan explores hereditary sickness (what agency does an individual have or is she at the mercy of her genetic code?), she refrains from naming and specifying the medical condition that afflicts both her characters. Such ambuiguity adds to the poignancy of the story. It doesn't matter, in the end, what Heather and Shelley suffer from; what's important is the effect they have on those around them.

Despite the serious ambit of The Paper House, shards of light penetrate the dark. The reviving effects of Heather's wild garden and the simple joy she takes in drawing her botanical subjects, as well as the generosity of her community of family and new acquaintances, provide restorative moments of grace.