"Fight Club" is about life in the Western world at the end of the twentieth
century. More specifically it's about what's happening to men in America.
The two main characters the nameless narrator, which I'll refer to as "Jack",
and Tyler Durden each represent one side of the increasingly divided American 
man. The narrator represents dull boring conventionality. Tyler on the other
hand is a man of action.

Jack is clever. Jack thinks too much. All work and no play make Jack a dull
boy. Jack feels sorry for himself. Jack is weak. This is how Tyler sees Jack.
Or rather how Jack idea of what Tyler thinks of him.

Jack's life is empty. He has many problems that he chooses to ignore. This
is probably what leads to his insomnia, a symptom of a greater disease. He
fills the void in his life by "losing himself" in the support groups. Fight
Club is the result of applying the idea of losing oneself to all aspects
of one's life. This is a recurring theme in the novel.

Jack loses time and gains time flying around the country. He loses himself
in the support groups. He is losing himself to Tyler who is taking over his
mind.

Tyler on the other hand is in control. However on closer inspection one finds
that he is not going anywhere Jack would want to go. In fact after the initial
excitement of fight club wears off, Jack is left in a pretty sad state. He
does not approve of the mayhem and destruction. He even tries to stop Project
Mayhem, which very nearly costs him his balls.

Tyler is not a leader of men. He leads space monkeys. At best he is the leader
of a successful cult.