Christopher Rowl and Christopher R.A. Morray-Jones, The Mystery of God: Early Jewish Mysticism and the New Testament (Brill, 2009), ISBN 978-9004175327
This is a great book synthesizing the vast amount study in the past few decades on early Jewish mysticism, with fascinating information concerning celestial ascent and the temple. However, being it's published by Brill, it has the ghastly price of $272. Aaaaaaarrrrrgh!
It is volume 12 in the Compendia Rerum Iudaicarum ad Novum Testamentum.