Vision: First thing to know is that you shouldn't take it so seriously. It's mostly a fashion-&-music subculture, though some -do- take it a bit more seriously than that.
Second, two books that helped me understand the basics are
'What is Goth?' by Voltaire and
Gothic Charm School by Ms. Jillian Venters. [Jillian also has a
website you may find interesting. =) ]
Welcome to the dark side! Here is a complimentary cookie with extra-dark chocolate. ^_^