I recently borrowed a book from my local library, titled "Our Gods Wear Spandex: The Secret History of Comic Book Heroes".
Written by Christopher Knowles, the book discusses the obvious and not-so-obvious origins and influences that gave rise to many comic characters and superheroes, some very popular (e.g. Superman, Captain America, etc.) and some not very well known.
You may find that you won't agree with all of the author's viewpoints (I didn't agree with his take on James Bond's Q's origin / inspirations - because I have other sources of references), but nonetheless, I have found this to be a very fascinating book, containing a lot of interesting information about the various influences that gave rise to some of the best known characters in today's comics.
I highly recommend the book to those who are interested in the history of comics, as well as those interested in learning the relationship between popular culture and society.
Wiki entry: http://en.wikipedia.org/wiki/Our_Gods_Wear_Spandex