The idea of Nagognog that this book caused more bad trips in the 1960s than anything else is an interesting one. Why might that be so? The book was intended to do the opposite:to prevent 'bad trips' by creating a positive guide to what was going on, and help the tripper through the potential difficulties. There are two things that I can think of. Firstly, it is a very precise and detailed guide, and (from what I've heard) most psychedelic trips are not predictable in that kind of way. Secondly, I don't think it would be suitable for most people on their first, or early kind of trip. You would need to be familiar with the general landscape of psychedelic experience before trying to use such a manual.
Recently, I have been reading the book in parallel with the Bardo Thodol, the original Tibetan Book of the Dead. It occurs to me that, if taken seriously, the book is a serious tome. It's about experiencing total reality, which is about as heavyweight as things come. It also makes clear that Leary, Metzner, and Alpert were, at the time, dead serious about the spiritual quest via psychedelics, and were able to verbalise awesomely some of what was going on. The book is on a high level spiritually. It is often forgotten, amongst the media hype and his own weakness for self-advertising, that Tim Leary was dead serious about psychedelics as a psychospiritual route. And one of the things that comes through to me on reading the book is how these guys were spiritual heavyweights. In its own way, this is the real thing.