The book begins in the archives here (Oct. 21, 2005): http://dresdencodak.com/2005/10/21/de-los-muertos/
And ends here (May 5th, 2010):
Essentially it's everything in the Dresden Codak archives up to Dark Science, excluding the first six strips. I wasn't able to include those because I was a reckless fool back then and drew them at web resolution. The shame!
In any case, it's over 80 pages of comics!