Baron Schwartz has put up a lengthy post describing what it's like to write a technical book (which I found through Matt Doar's smaller, but more graphical, post). I'm doing this for the fifth time right now (two solo, two edited, the current one collaborative). I haven't been keeping a word count log for this one, but I did for Data Crunching (and I used to for my fiction, back when I was actually writing some), and I found it a great way to keep myself honest. I also found the big downward spikes showing days when I did nothing but rip out inadequate text rather therapeutic... :-)