Well, I finished this book a month or two ago, so I'll give you my thoughts.
It's an entertaining read, but definitely not a "classic." Pinchbeck mostly summarizes the history of the psychedelic culture and throws in a few trip reports and his experience at Burning Man. His analysis of the history of the culture seems rather provincial, and anyone interested in learning the history is better off reading Leary, McKenna, etc., unless they don't have the time and simply want a quick, brief overview of it all.