I'm going to begin this review by explaining what the book is NOT about, since a number of reviewers seem to have been disappointed by what it contains. I will also include where to find information on some these topics.
"Giordano Bruno and The Hermetic Tradition" is NOT a biography of Bruno (1548-1600), who, according to the common view was burned at the stake for teaching Copernican astronomy (this was one of the charges, but was a side issue). There is a need for a modern biography, but this volume, first published in 1964 -- not, as the listing suggests, 1991 -- was a contribution to understanding Bruno, and not intended as a full account.
(Amazon gives the date of the current University of Chicago trade paperback; there was also a similar Midway Paperback edition in 1979, and a 1968 mass-market paperback edition, as well.)
It is NOT a study of the traditions surrounding Hermes Trismegistus ("thrice-great Hermes"), a Greco-Roman version of the Egyptian god Thoth and the Greek Hermes, among other things, who has had a long history in Western (and Islamic) tradition; it discusses some of them, in the context of Renaissance and Reformation Europe. Collected papers by Antoine Faivre, "The Eternal Hermes: From Greek God to Alchemical Magus," translated by Joscelyn Godwin, now approximate such a full account (paperback, 1995).
It is also NOT an historical account of the Greek and Latin (and Arabic, and some other) mystical / philosophical, magical, and alchemical texts purporting to be the works of Hermes and his disciples. For that, the historically-minded can turn to Garth Fowden's difficult, but rewarding, "The Egyptian Hermes: A Historical Approach to the Late Pagan Mind" (1986; with new Preface and corrections, as a MYTHOS paperback, 1993). The curious may also look to David Frankfurter's "Religion in Roman Egypt: Assimilation and Resistance" (also a MYTHOS paperback, 1998) for a fuller context in popular religion. Those who want to adopt Hermeticism as part of their personal religious experience may need to go elsewhere.
It is NOT a translation of those ancient texts, some of which it summarizes for the reader unfamiliar with this rather obscure literature. For those important in Yates' account, see Brian Copenhaver's "Hermetica: The Greek 'Corpus Hermeticum' and the Latin 'Asclepius' in a new English translation, with notes and introduction" (1992; in paperback since 1995). The testimonies (references in other writers) and fragments (mainly excerpts preserved in a Byzantine anthology) are in the four-volume "Hermetica: The Ancient Greek and Latin Writings ..." (1924), edited and translated by Walter Scott (not the novelist). Yates warns against his high-handed editorial treatment of the main texts, but the testimonies, and most of the fragments, are given in more conservative forms; this too is (or was) available in paperback.
It is NOT an account of the Western Occult tradition in the Renaissance, with or without instructions for the would-be practitioner. For an account of the main texts and issues, the curious can begin with Yates' main authority in this matter, D.P. Walker's "Spiritual and Demonic Magic from Ficino to Campanella" (1958; there is a recent paperback). Walker and others are critically reviewed, with new hypotheses, in Ioan P. Couliano's "Eros and Magic in the Renaissance" (1987); a different perspective, and some important corrections to Couliano's data, are found in Noel P. Brann's "Trithemius and Magical Theology: A Chapter in the Controversy over Occult Studies in Early Modern Europe" (1999; both in paperback).
That being the case, what IS "Giordano Bruno and the Hermetic Tradition," and is it worth reading?
Yates claimed that the book began as a translation of Bruno's Italian dialogue, "La Cena de le Ceneri," set in Elizabethan London, and grew. (The dialogue has since been translated, with useful notes, as "The Ash Wednesday Supper," by Edward A. Gosselin and Lawrence A. Lerner (1977; a Renaissance Society of America Reprint Texts paperback, 1995).
The book is an attempt to restore a missing, or at least neglected, chapter, in Western intellectual history. The "Hermetic Tradition" in the title is the set of beliefs about the supposed Hermes Trismegistus which Renaissance Europe inherited from the Church Fathers. They variously saw him as an ancient Prophet, and the real source of Plato's philosophy, and perhaps the disciple of Abraham or Moses, maybe even their teacher; or as a wicked tool of Satan. When Greek manuscripts of supposed Hermetic texts became available in Florence, the Medici put a priority on translating them, instead of Plato or Plotinus, and Marsilio Ficino obliged, launching a wave of excitement among some European thinkers.
What these thinkers, including, but not limited to, Bruno, did with, and to, the material they were given is the burden of the book. The enthusiasm eventually went underground, especially as it came to be realized that the wonderful Hermetic texts were not only post-Platonic, but post-Christian. This view took centuries to permeate European thought, however, and true believers in the Hermetic texts are still around. ("The Magic Flute" is just one example of originally Hermetic ideas about Egypt surviving into the Enlightenment.)
Bruno himself knocked about Europe, promoting plans for reconciling Catholics and Protestants, spending time -- not very happily -- in Elizabethan England. The Holy Office of the Inquisition eventually became aware that his plan seemed to involve the restoration of Egyptian Sun-worship -- the True, Original Religion of Mankind, as revealed by the Divine Hermes -- in a Christian cloak. There was also more than a hint of plans to use magic, and astrally empowered images, to achieve this and other goals. The heliocentric theory was for Bruno, it seems, just one more proof of the divine nature of the Sun. One can understand their indignation.
It is this Bruno, the Hermetic, the Magus, and the very amateur scientist, which is Yates' centerpiece. She continues the story with some latter-day Renaissance Hermetics, including Campanella (whose utopian "City of the Sun" seems to have revived, perhaps independently, some of Bruno's pet projects).
As someone who was a college student in the early 1970s, I can recall the impact in several areas of this book (then in its 1968 Vintage Books mass-market paperback), and its 1966 follow-up on another neglected area of European history, "The Art of Memory." Although in later writings Yates tended to leap from bold insights to unsupported conclusions, these two volumes helped rewrite the way a generation of historians would look at the European past. Some of the volumes I have mentioned would not have appeared, or would have been very different, without Yates' contribution. And yes, although not a complete portrait of either Bruno or Hermeticism, the book is still worth the reader's time and attention.
[Note, August 2005; a complaint by a more recent reviewer sent me back to take a close look at my copy of the 10th printing (1999), which is, as I remembered it, cleanly printed, with the plates as well reproduced as in earlier versions (some were made from not-very-good period originals!). Anything less, especially smudged or bleeding print, missing text, etc., as described, should be treated as a manufacturing defect, and the copy, if purchased new, should be returnable for this reason. (Or so I would think.) The University of Chicago Press certainly can do better, and usually does.]