North Americans are the world’s most prolific users of opioids. In On Opium, Zwarenstein describes her own use of opioid-inspired medicines and evokes both Thomas De Quincey and Frida Kahlo as she travels from the decadence of recreational drug use in past eras to the misery and privation of the overdose crisis today. She investigates why people use substances and when substance use becomes addiction. And she exposes the effects of poverty, isolation, and trauma; the role of race, class, and gender in addressing pain; and a system of prohibition that has converted age-old medicines into taboo substances. Through all of this, Zwarenstein finds hope. Drawing on solidarity between illicit drug users and people in pain; in a wise understanding of what humans need to be well; and in radical drug policies like legalization and safe supply, she lays out a vision of a world where suffering is no longer lauded, and opioids are no longer demonized.