Scott Rosenberg, the co-founder of Salon, has written an excellent new book called Say Everything: How Blogging Began, What It's Becoming, and Why It Matters.
It's well-researched and very entertaining. Scott interviewed me last year and there's an entire chapter about Boing Boing in it. He also has chapters about Justin Hall (who started the blog Links From the Underground in 1996), Dave Winer, Jorn Barger (who coined "weblog" for his Robot Wisdom blog), Blogger founders Ev Williams and Meg Hourihan, and Heather Armstrong of Dooce, among others.
Above, an interesting video in which Scott tries to identify the very first blogger. It's sort of like trying to find the first rock'n'roll song.