Well, there are really good bits and some bits that the book could easily do without.
Shura's own parts are pretty good, albeit not a literary gem. Quite frankly, for me as a physicist the most entertaining part was to see glimpses of how organic chemists work, the thought process itself. Trip reports and that sort of stuff, I've had better, but still OK, especially given the variety he's been going through... The cookbook can be fascinating if you have no idea how organic synthesis works in general - just reading through the methodology can be a page-turner.
Now, Alice's parts (half the first part of the book, give or take) - wow. Not in a good sense. Self-obsessed, centered pointlessly around Shura's affair with another woman to start with and later on drifting towards strikingly shallow para-philosophy, it would be more at home among Danielle Steele's paperbacks with so little attention given to the book's subject matter. Perhaps it's me who's missing the point and there's a good reason why a couple of hundred pages in the book are more or less dedicated to what Alice thought about Ursula, that other woman. I just don't see what phenethylamines have got to do with it.
So overall if you're looking for something along Castaneda's lines with more scientific slant on it, I don't know, I would say keep looking. Shulgin is Shulgin, a genius of a chemist, but his wife ain't one and it's her contribution that spoiled it for me.