With legal cannabis sales at $5.4 billion in 2015 and expected to rise by another billion this year in the United States, legalization and marijuana’s impact on health is a hot topic of national debate. Casarett, a physician at the University of Pennsylvania, immerses himself in the culture, science, and smoke of medical marijuana in order to sort out the truth behind the buzz. Our reviewer, who has authored more than 120 research papers and reviews on the regulation of synaptic inhibition and endocannabinoids, tell us what the author got right, but also overlooked on his journey to learn more about a complex and controversial subject.