This book, while not especially well done, opens up the doors to talking about the structure of superhero stories. Reynolds essentially argues that there are central elements to a superhero story that all narratives must follow, and if they chose not to follow, they are drawing attention to that aspect of the narrative.
For instance, he argues that all superheroes must have an estranged relationship with their fathers. Superman never knew his parents, Batman's parents were killed in front of him, Spider Man was raised by his uncle who was killed by his own choices, the X-Men have troubled relationships with their parents. This makes sense. There are few superheroes that have any valid relationships with their fathers, or the mother, for that matter. Those that are fathers (Reed Richards, Wolverine, etc.) have issues with that role, torn between their duty as superhero and their duty as father.
While, like this, a lot of his observations make sense, and can be traced through the mass of the comic canon, Reynolds tends to pull up just short when examining these elements. For example, he goes on about the costume choices, noting that the costume is essentially a new identity for the hero. This new face (see Rorschach in Watchmen), then, provides the hero with the identity that often time lacks in the heroes real life. Reynolds makes this claim, more or less, and then fails to provide any tangible evidence. He makes a good point: the costume tradition is a language, the individual costume is the utterance; but to what end? When Spider Man switches from the blue and red Spidey Suit to the black suit, things change for him. The blue and red, much like the first hero, Superman, are the colors of good. Spider Man, regardless of the harm to him, or the opinion of the paper, does good in those colors. Under the symbiote Venom, he is much different. The lines between right and wrong are blurred, his actions take on a more selfish feel. The first clue that this is a new take on and old form is the costume.
There are hundreds of other examples: Rorschach from Watchmen, Batman and Superman (he does touch on this, but not hardly enough, since Batman goes through several costume changes, especially in Batman: The Dark Knight Returns, one of Reynolds "important" texts), Elijah Snow from Planetary, Wonder Wart-Hog...the list goes on. Not to mention all that can be made from the women's costumes (again, he touches on this idea, but never enough support is supplied, nor does he fully explore the idea).
Like Scott McCloud and Understanding Comics, Reynolds gives us a base to build from. As far as this project is concerned, there is so much ground to be covered. A lot has happened since the publishing of the book, and more can be made of the foundation, sturdy but lacking, that Reynolds has laid.