I was excited to pick this book up as a fan of the writing of Huxley and interested in his first-person account of mind altering drugs. A lot of the information and insights given are predictably fascinating-- getting into the science of what peyote and similar drugs do to the brain, in terms of 'removing' filters and opening the mind up to perceptions that are always under the surface. Hearing Huxley's firsthand account as he takes the drug and is carefully observed by his writer friends was compelling, and the second half (Heaven and Hell) goes a bit further to get into why the human brain sees and perceives the things it does without drugs (though our understanding of it is increased by observing it on the drugs). A lot of interesting insights into the function and psychology of the brain, and the book was not a long one, but it really read as simply two essays that dragged a bit on without any natural stopping points in the middle. This made it a bit unreadable and harder to continue to come away with a satisfying chunk read with insights gained.