Wildbow: I don't think it's book related. The book came out in July 2012. I didn't see much of a change then. I do sell more books when I'm getting more readers though. Legion's always grown through a combination of links from other authors who linked to the story, directories (WFG, Muses Success, and--originally--Pages Unbound), a little bit from fan fiction sites, and also a small, but constant amount of advertising by me.
Basically I spend a maximum of 10 dollars a month on Project Wonderful. I initially spent more than that (30? 40?) in spring 2010, and it actually had enough of an effect that I've continued at a lower level ever since.
Here's a graphic of my site's overall growth. You'll note that it's not a straight upward climb, but the direction is consistent.
Alice: For the first six month of my serial 40 page views a day was pretty typical (and even by the end of a year, 40 wasn't impossible). Now, I get more than that entire year of pageviews in a typical month. It's largely a matter of time. More people link to me now, and thus I get more people investigating and reading.
In my first and second year, I had roughly 500 pieces of comment spam--practically nothing.
Ubersoft: Thanks. I'm sure your webcomic passed that point a while ago.