How does Chuck Palahniuk create suspense, superb action, and twists in Fight Club?

Fight Club is a very suspenseful novel with multiple plot twists that keep the reader guessing throughout. In fact, it is probably mostly due to these twists that the book, and then film, became so popular. So, how did the author create these? What works?
First and foremost, it is not immediately apparent to the reader that the narrator has more than one personality. The book opens with the narrator and his "friend," Tyler Durden, on top of a building. Tyler has a gun in his mouth. This would cause the reader to expect that these two men are two different people, not two different personalities of one man. It is not until farther into the book (where and when varies for each reader) that it becomes obvious to us that the narrator and Tyler are different sides of the same person. Because the reader does not know this to begin with, many of the plot twists in the book are more interesting and suspenseful, and when it is finally obvious to the reader that Tyler and the narrator are the same person, that is the most interesting plot twist of all.
Second, the unpredictability of the characters keeps the readers in suspense about what will happen next. The book's narrator is unreliable not only because of his mental illness but also because he leaves out information when he tells us what happened. He doesn't always know what happened or why. For example, he knows that Tyler and Marla are having a sexual relationship, but he never sees them in the same room together. This is an indication to the reader that Tyler is another personality of the narrator's, but for those who have not figured it out yet, the reader only knows as much as the narrator knows at any given moment—and his knowledge is very limited.This limited knowledge means he has no way of knowing who will do what and when, so everyone's actions are unpredictable. On top of that, the actions of Tyler and Marla are often irrational, making them even more unpredictable.