Kabbalah: A Very Short Introduction by Joseph Dan

Another in the "Short Introduction" seriers, this one runs about 130 pages. It turns out to be mostly an historical perspective, rather than a "how to" or a "how does it work." The history of the Kabbalah has been deliberately confused from the Middle Ages on, both to obscure it's origins as separate from early Biblical and Talmudic writings - and to keep it from easy reference by by those not educated, enlightened or serious enough to understand it's secrets.

Next, Dan traces the Kabbalah in parallel with other Jewish developments, as well as Hadisim, Gnosticism, and an interesting subject the author refers to as "Christian Kabbalah." Madonna is mentioned in a section about a corrupted, commercialized, new age version - that is similar to Kabbalah mostly only in name.