The book offers a simple, down-to-earth, overview on the most important alchemical theories, which is done in its first half (or less). The rest is about the most notable alchemists. From then on, the book gets really summarized, shallow and dull. But I guess this unfortunate unfolding would not be badly explained by bearing in mind the original intention of the author, which is, to interpret Alchemy as the flourishing chemistry, that is, its extrovert side, as Jung would fairly put it. And he does that with rare respect to these magic pioneers.
Much of what is taught in this book is elsewhere concealed within the majestic veil of allegory. So I guess it's worth to be looked into.