THREE BOOKS ON KABBALAH are reviewed in the Times Literary Supplement:

Kabbala then and now
Jeremy Adler
Daniel C. Matt
THE ZOHAR
Pritzker edition
Volume One
500pp. 0 80474747 4.
Volume Two
496pp. 0 804 74868 3
Stanford University Press. $49.95 each; distributed in the UK by Eurospan. £29.95 each.
Arthur Green
A GUIDE TO THE ZOHAR
191pp. Stanford University Press. Paperback, $15.95.
0 8047 4908 6
Moshe Idel
KABBALAH AND EROS
371pp. Yale University Press. £25 (US $45).
0 300 10832 X

More than just a review, this is an essay on Kabbalah, its background, the history of modern scholarship on it, and the current state of the question. Merkavah mysticism and Hekhalot literature also get a mention:

This evocative, light-filled imagery and the vision of a heavenly throne in which it culminates gave rise to the most ancient form of Jewish mysticism, so-called merkabah or “throne” mysticism. The doctrine was apparently established by the period of the Second Temple, and the key documents concerning this journey of the soul stem from the period before the expansion of Islam: as in related traditions, upon performing sundry ascetic rites the mystic approaches the Divinity, in this case after a journey through His “seven Heavens” into the “seven palaces”, until he finally witnesses the manifestation of His glory on the “throne”. Unlike the literal truths in the Pentateuch, a text like Ezekiel that enshrines this mystery demands to be approached symbolically, a mode which could hardly differ more sharply from that required by the law. Thus, whereas the Talmudists interpret the Bible rationally, expounding the laws in a continuous dialectic by adducing other parts of the Bible as evidence, the mystics read the sacred Book the other way round: they begin with the visionary mode in Ezekiel and treat the earlier Books as symbolic. This enables them to search behind the literal truth.

This is basically right, although it's hard be sure exactly when the key documents took the form(s) that we have now. Some of the material clearly goes back at least to the fourth century, and many of the key ideas to the Second Temple period. But the texts continued to be heavily edited well into the Middle Ages and some of the material -- it's hard to say how much -- must be medieval. We're only in the early stages of understanding the history of the texts and their transmission. (I'm thinking about such matters a lot right now, since I'm writing the "Merkavah Mysticism" article for the New International Dictionary of the Bible. I also gave them the "Enoch, Third Book of" article earlier this month.)

Anyhow, this TLS piece is a very good brief introduction to Kabbalah. Read it all.

(Via the Agade list.)