Progressive Ruin:
Longtime readers of this site know my experience with this...movie-related comics tend to peak in sales just before the movie's release, before dropping down to pre-movie hype sales (or even lower) upon or shortly after the film's debut. It happened with V for Vendetta, the first Spider-Man movie, From Hell, League of Extraordinary Gentlemen, and so on. And, judging by customer demand, trade sales could have been bumped upwards by the Sin City and Hellboy movies, but since Dark Horse was incapable of supplying those books to the direct market during peak demand, that's all theoretical.
The Watchmen movie is the real test, however. The Watchmen graphic novel has been a consistent, constant seller for years. I don't have the numbers right in front of me, but I imagine it probably outsells several new graphic novels from Marvel and DC in any given month. It has a legendary status within the hobby, and at least some minor amount of recognition outside the hobby. I'm still reordering copies every week...and just when I think that there's no possibly way everyone hasn't read this book by now, I sell more copies.
Now, at this point there's little chance that this movie is going to sink without a trace. It's a big-budget superhero movie, and it's gonna get noticed by the general public. Sometime late next year, and especially early '09, we're gonna be sick of seeing that smiley-face-with-blood-splash symbol all over everything advertising this flick. So, this movie will almost certainly enter the public consciousness.
If the movie's good, the comic will become superfluous. "I've seen the movie...I don't need to read the comic." If the movie's bad, it'll be people in the store pointing at the book on the shelf and saying "Oh, yeah, Watchmen...that was a crap movie. Look, there's a comic based on it!" And then they'll laugh. (This is also known as the "League of Extraordinary Gentlemen Effect.")
I exaggerate slightly, but not much. V for Vendetta still sells, for example, but not nearly at the numbers it used to. I expect something similar to happen to Watchmen. Hopefully the movie will be at least watchable, so I don't have the additional burden of trying to convince customers that, yes, this comic is good, no really, it's not like the movie. (This is known as the "Howard the Duck Effect.")
