so if there is a movie that you don't fully understand, and want to attempt to understand it more, you should..

read the book that it was created from

I personally loved fight club, the movie, but the book was even better, and gives you a better perspective on the story, as usual..

you probably really don't like the movie because so many people like it and you feel you should like it so you have expectations for it that it doesn't live up to..

anyway, in general i'd just say the story is a product of superficiality in society and how Ed Norton's character is so numb to his everyday life because it is so meaningless.. and he can't sleep.. So finally when he goes to these meetings, he is able to sleep.. until Marla comes along..

and then you have the creation of fight club, to bring some meaning into ed nortons characters life.. He was so numb to his everyday routine, his everyday sequence of going to work, that he eventually, mostly through his insomnia wished he could be someone else (tyler).. and did become that person.. and brought a self-destructive lifestyle to his life to add some meaning and excitement to it.. It was it's own form of therapy.. in fight club you became someone else..

that's my interpretation of a general theme of the movie..