Funny but I just watched it the other day too and finally managed to grab a copy of the graphic novel for long enough to read it properly - I've browsed it for years, but never bought it. The novel is a lot denser, grittier and has to be read carefully to catch the cross-webbing that Moore and Gibbons managed to string together. A movie couldn't capture that - and it didn't - but I think the film was pretty damned faithful to source and a good flick (Oz slang) to boot. In some ways the movie rectified certain implausible features of the novel - eg. Ozymandias framing Dr.Manhattan as a threatening 'World Destroyer' makes more sense than the 'Thing from another Dimension' scam in the novel, tho that echoes the late RR's comments from the time on the USA/USSR banding together to fight off alien invasion.