Simply put, it is not precisely a religion as there is a distinct lack of a deity. The belief structure is somewhat complicated but boils down to this. There is a grand villain of the galaxy, who at some point loaded up a bunch of malcontents and sent them to earth on spacecraft that resembled contemporary (at the time) aircraft. Upon their arrival they died. Their "spirits", however, linger and infest pretty much everything. The various maladies of life (seriously, just name one) are caused by said spirits. The religion is based upon the notion that cleansing one's self of these spirits will improve their lot in life.
Even if you don't believe such things, the basic structure of said religion is designed to make it necessary to the believer. This is generally true of any religion one cares to mention. In exchange for money, time and effort the church will endeavor to reduce the incidence rate of these malicious spirit in your body through measures that are not entirely clear. From the outside, it (like any religion if one takes a few steps back) is a pyramid scheme and a play for power and control. Its belief structure is fairly silly but then no more so than any other I've heard of.
Strangely, here in Austin, there is a Church of Scientology directly across the street from the University of Texas. It seemed a terribly strange place to put a church. I myself am curious about the religion - not because I believe any of it but because it has ensnared so many people. This fact alone makes it fascinating but I suspect I'll never walk through the door. I know little about what transpires and I know less about my own weaknesses. I don't think I care to have them exploited by others, especially when I, as a logical man, suspect I have little to gain.