The Celestine Prophecy is an interesting book to say the least... Try to get your hands on the flick What the Bleep Do We Know.... Dabbles in the connection between Quantum Physics and the actual capabilities of the human mind. (The energy of thought and power of mind over matter type of crap) Kinda hokey in production.. but the concepts behind it are what make it.
Journeying is kinda just like putting yourself in a trance... similar if you've ever tried to hypnotize yourself. Except.. I've experienced a feeling of being yanked up really fast, ... as if someone was dragging me up by the back of my tshirt. (not to mention the stuff expereinced during the actual "journey")

Weird. But cool. Deffinatly opens up your mind more.