Last week I finally got around to reading Understanding Comics (1993) by Scott McCloud. This is one of those books that has been in the back of my mind as something I would like to read for years, and yet I never did. Now that I have, I'm really interested to check out McCloud's other books.
In Understanding Comics, McCloud uses the comic form as a vehicle for explaining a sometimes rather technical and philosophical view of what makes a comic a comic, how reading comics is different from watching a movie or reading a book, and how comics work in general. There is a wikipedia entry on this book that quotes McCloud's arguments extensively and gives the flavor of the thesis of the book (although the author of the page seems to run out of steam about halfway through, and accurately acknowledges that the arguments read much better in McCloud's comic form).
For me, one of the most interesting parts of this book was McCloud's Big Triangle -- a graphical exploration of the continuum between cartoon and realism and abstraction. It is an intriguing way of categorizing and comparing different comic artists without passing judgment on their artistic or narrative styles.
Finally, reading this book really made me want to check out some of McCloud's fictional comic art. I happened to come across a link on BoingBoing to the first two parts of his online comic The Right Number, which is presented in a compelling Flash style that really takes advantage of the online comic format without taking away from the still nature of graphic novels (this isn't an animation, after all). I hope part three is released soon...