A groundbreaking meditation on pain, painkillers, and dependence from a prescription opioid user. Her writing has been described as "measured," "sensuous," and "compelling." In 2016, Carlyn Zwarenstein's short narrative on pain made the Globe and Mail'sTop 100 Books. Now, she returns with a seductive dive into opioids and the nature of dependence. North Americans are the world's most prolific users of opioid painkillers. In On Opium, Zwarenstein describes her own use of opioid-inspired medicines to cope with a painful disease. Evoking both Thomas De Quincey and Frida Kahlo, she travels from the decadence of recreational drug use in past eras to the misery and privation of the overdose crisis today. Speaking with users of prescribed morphine, illicit fentanyl, and smoked opium, Zwarenstein investigates uncomfortable questions about why people use substances and when substance use becomes addiction. And she exposes causes of drug-related harms: the debilitating 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.