For most comic book adaptations, being different from the books is bad. "Different" usually means studio execs decided they knew better than the creators of the comic book in translating it to the silver screen. Ironically, the end result of "different" is not so different at all, as many an awesome comic book has ended up a standard piece of Hollywood cheese resigned to a bargain bin DVD for the rest of its days.
"Scott Pilgrim vs. the World" is not the first good comic book adaptation. There's been plenty of them dating all the way back to the original Superman with Christopher Reeve. What makes "Scott Pilgrim remarkably different is how it succeeds in compressing all six books of Bryan Lee O'Malley's award-winning graphic novel series into one 112 minute movie while still staying largely true to the books.
Director Edgar Wright - of "Shaun of the Dead" and "Hot Fuzz" fame" - does all of this without pandering to a shot-by-shot adaptation of the comic book. Since he's adapting six manga-sized graphic novels, that just isn't possible all the time. Wright does lift plenty of sequences straight from the comic book, but he also makes foundational changes which improve the flow of the film as a single narrative - such as making big-bad Gideon a sought-after record producer, and enhancing the video game elements referenced in the books. For the most part, these changes all pay off - though the final fight is a bit too long and slightly less original than its comic book counterpart.
Ultimately, my one biggest complaint (other than the casting of Michael Cera as Scott Pilgrim) isn't so much with the film as it is its reception. I've told people plenty of times - if you like this movie, you should read the books. And the response is generally, "But the books are just like the movie . . . right?" It becomes frustrating because comic book fans have been trained to expect any movie different from the source material to be typically inferior - which just isn't the case with "Scott Pilgrim." Yes, there is more character development in the books as opposed to the movie, but the books cover just over twelve hundred pages of material. It's like if your favorite new band covered your favorite old band's songs - with the old band's remaining members helping out. It would probably sound good - but of course it would sound different.
As comic books continue to receive more respect from other mediums, we'll hopefully continue to see more even conversations on the translation of comics books to movies and beyond. So bottom line: if you like the movie "Scott Pilgrim vs. the World", you really should read the books - and vice versa.