If you are a journalist or a young researcher with an interest in political blogs, you might want to check out this book. It gives a rather comprehensive and systematic overview of research results and popular thought on blogs and their role in a democracy.
For an elaboration on the strengths and weaknesses of the book, see my blog (on my profile)
The bottom line is this: The volume is a solid intro into the political blogosphere for the researchers starting to examine blogs; it also might be thought-provoking for those researchers who've studied blogs for a while. Overall - I'd recommend buying and reading the volume. The volume is among very few books out there that deal with new communication phenomena in a systematic manner.