An addict trapped in a country house becomes obsessed with vacuum cleaners and the people who sell them door-to-door. An abandoned woman seeks consolation in tales of armed robbery told by one of her fellow suburban housewives. An accidental mother struggles to answer her daughter's badgering about her paternity. And in three stories readers meet Louisa, a woman with Down syndrome who serves as an accomplice to her younger sister's sexual exploits and her aging mother's fantasies of revenge.

Together, Happiness Is a Chemical in the Brain is a sharp-edged, witty testament to the ambivalence of emotions, the way they pull in directions that often cancel one another out or twist their subjects into knots. In lyrical prose, Perillo draws on her training as a naturalist and a poet to map the terrain of the comic and the tragic, asking how we draw the boundaries between these two zones. What's funny, what's heartbreaking, and who gets to decide?