We get Eddie Willers. In a book filled with larger-than-life heroic figures, living legends, moral strikers, destructive "looters," and industrial giants, Eddie is just a normal guy. He works a decent job at the railroad, nursing a long-time crush on his best friend from childhood. All of which leads us to ask: what on earth Eddie is actually doing in this novel in the first place?
The answer is that Eddie is playing the role of the everyman here. He's the decent guy who hates the villains without himself being a hero. As the regular guy just trying to survive, Eddie also provides readers with a much needed "in" to the story. Eddie asks the sort of questions that people do when they're trying to figure out a mystery that seems light years beyond them – which is exactly the position the reader is in at the beginning of the novel. As an average Joe, Eddie represents a whole country of decent people who have the bad luck to be living during rotten times.
Aside from being exceptionally unexceptional, Eddie the everyman also provides us with some fresh perspective on the book's major themes and ideas.
Functioning as our "in" to the story, Eddie often gets saddled with a lot of the book's exposition: the factual, introductory details that clue us in to what's going on. While everyone else is busy speechifying and thinking Deep Thoughts, Eddie gives us the facts.
Most of our scenes with Eddie involve him having curiously detailed one-sided conversations with a mystery railroad worker, whom we later find out is John Galt. These conversations not only provide us with facts and bring us up to speed when the narrative jumps ahead in time; they also give us a lot of insight into Eddie, Dagny, and Galt himself. Eddie confesses his fears, his feelings for Dagny, his love of the railroad, etc. in these conversations, which often take on the form of a confessional.
It's oddly fitting that Eddie is the person involved in these conversations, which help anchor jam-packed chapters. Eddie is often our only link to Taggart Transcontinental, since both James and Dagny are frequently depicted elsewhere. He's a valuable source of Intel on various characters and major events.
It's also worth noting that Eddie actually has a personal relationship with John Galt, even though Galt never really talks about Eddie. Aside from the Taggart siblings, the only other people we really see Eddie interact with in the novel are Francisco (via flashbacks), Hank, and John. This is notable, because it shows how much Eddie's character is filtered through Dagny's. All of the people he interacts with in the book are major figures in Dagny's life, and he's often talking to them about her. Eddie is a bit like Dagny's shadow, really. So let's look more closely at Eddie's relationship with the Taggarts.
The Taggarts are central to understanding Eddie's identity. James Taggart, being a jerk as usual, calls Eddie the Taggarts' "feudal serf" in Chapter 1, and Eddie doesn't deny the characterization. Apparently the Willers family has always worked for the Taggarts. Eddie grew up playing with Dagny, who is two years his senior, and has clearly always worshiped her as a hero:
That day, in a clearing in the woods, the once precious companion of his childhood told him what they would do when they grew up. The words were harsh and glowing, like the sunlight. He listened in admiration and in wonder. When he was asked what he would want to do, he answered at once, "Whatever is right," and added "You ought to do something great...I mean the two of us together." "What?" she asked. He said "I don't know. That's what we ought to find out. Not just business and earning a living."... What do you suppose is the best within us?" "I don't know." "We'll have to find out." She did not answer; she was looking away, up the railroad track. (188.8.131.52)
Eddie loves Dagny, and throughout the novel he clearly favors her values over those of people like James. James confuses and frightens him. In fact, Eddie frequently confides his distress about the state of the world to Dagny, wanting her to reassure him and explain it all to him. But Eddie doesn't just use Dagny as a shield; he's also fiercely protective of her, as he reveals in one of his conversations with Galt:
"It's not so bad for me in the daytime, because I can keep busy and not think, but it gets me at night. I can't sleep anymore. I lie awake for hours.... Yes! – if you want to know it – yes, it's because I'm worried about her! I'm scared to death for her!" (184.108.40.206)
So if Eddie shares Dagny's values, and is no friend of the looters, then why isn't he invited to participate in the strike? Did his invitation get lost in the mail? Galt spent all that time talking to him and still didn't offer to help Eddie out? What gives here?
To answer that, we need to look at Eddie's personal values and at his important role in bookending the book.
It is fitting that Eddie Willers begins and ends the book for us. He's the first person we meet, in a sequence that sets in motion the novel's ongoing mystery (what's happening to the world and who is John Galt?) and introduces a feeling of ominous doom that lingers throughout the novel. We experience dread most acutely through Eddie, the average guy who doesn't have the answers or the tools to change things.
Eddie Willers walked on, wondering why he always felt it at this time of day, this sense of dread without reason....It's the twilight, he thought: I hate the twilight. (220.127.116.11-12)
Eddie introduces us to the theme of encroaching darkness here as well, both metaphorical and literal. Galt's strike is seeking to "extinguish all the lights" after all. To see why Eddie wasn't able to, and in terms of the narrative could not escape the darkness, we need to look at his unrequited love for Dagny and at his final scene.
When they were gone, he felt what one feels at the loss of a dream one had not known till after it was lost. (18.104.22.168)
Then suddenly he felt the blinding surge of a desperate, righteous anger. He leaped to his feet, seizing the throttle. He had to start this train; in the name of some victory that he could not name, he had to start the engine moving....Don't let it go! his mind was crying....He was pulling at coils of wire, he was linking them and tearing them apart....He heard himself crying soundlessly – Dagny, in the name of the best within us...I must now start this train! (22.214.171.124-82)
Poor Eddie always realizes things too late. He sees his "dream" for what it is only after it is gone. He's always been a few steps behind Dagny, and when the country collapses he is no longer able to follow her. It's tragic and cruel, but it also serves a larger purpose in the narrative: Eddie represents all the people who were left behind by Galt's strike and were royally screwed by the looters' regime. Eddie needs to be where he is at the beginning and the end of the novel, since it's through him that we experience the devastating effects of a country in collapse.