Not just about an utterly fascinating topic (psychadelic drugs), in terms of history (LSD turning from a scientific wonder drug to illegal), his personal experiences, and the neuroscience behind it, but also just extremely well-written -- a real page-turner. A crazy potent combination of science, spirituality (from a skeptic), and narrative. I expect his book will be a significant part of why psychadelic drugs will be legalized in the near future specifically for therapeutic purposes.
Also +1 for 2017's Why We Sleep [2]. After reading it, I couldn't believe how shockingly ignorant I'd been of how I spend a full third of my life, and how much it affects the other two-thirds -- and the degree to which a lack of sleep prevents us from perceiving the effects of lack of sleep, in a kind of vicious cycle.
[1] https://www.amazon.com/Change-Your-Mind-Consciousness-Transc...
[2] https://www.amazon.com/Why-We-Sleep-Unlocking-Dreams/dp/1501...