WTH is Gnosticism?

In reading Invitation to a Beheading by Vladimir Nabokov (writer of Lolita), my literature class got into a discussion on what gnosticism is. (Read the Wiki on Gnosticism here.)

For almost all of my entire adult life (Which isn’t that long, really. Just trying to make a point here.), I have been trying to get my head around the concept of the Supreme Being. Organized religion seemed to me an inadequate source of information, science was too critical of the Divine’s existence, and all philosophy only showed me that both sides of the existence argument could be true. I settled with being deist, which isn’t really saying much. When I heard about gnosticism, I decided to read about it, hoping, I suppose, to get better answers than I’ve had thus far.