Watchmen

No doubt some purists will hate this double-disc special edition DVD, for much the same reason that they hated Zack Snyder's film Watchmen - because they cannot brook any alteration being made to the beloved 1985 urtext by Alan Moore and Dave Gibbons. Such folk may prefer to wait for the inevitable multi-disc edition that incorporates Under The Hood and Tales Of The Black Freighter (cut from the film and currently available on a separate DVD), or they may wish just to stick to the original graphic novel rather than grumble about this or that minor plot change or character adjustment instigated by the meddling Snyder.

For the rest of us, though, less proves to be more, and Snyder's epic is sprawling and complex enough as it is without the need for endless additional episodes and subtexts (better suited to the printed page), or for apocalypses that come in outdated tentacular form. Many may even be relieved to see that this 162-minute feature is not accompanied by a traditional director's commentary, but rather by a series of 11 bite-size 'video journals' which collectively offer a detailed yet palatable mosaic of the production in all its aspects, from set design to costumes (in multiple periods), from models to stuntwork, from special effects to colour palette, and from motion-capture performance to CG work. Visiting the set and witnessing the spectacle of his illustrations from over two decades ago being brought to life, a visibly excited Gibbons declares: "It's like a full realised, crystallised dream."

The remaining extras adopt an oblique approach to the film and its themes, but are no less revelatory (and interesting) for that. Mechanics: Technologies Of A Fantastic World (16 minutes) engages James Kakalios - "mild-mannered physics professor of the University of Minnesota", author of The Physics of Superheroes, and consultant on Watchmen – to discuss the real science (or otherwise) behind Dr Manhattan's blue glow ("Cerenkov radiation") and power over his own "quantum mechanical wave function" (a "miracle"), Nite Owl's flying vehicle and goggles (the latter now "very routine" but "a little bit ahead of the curve in 1985"), and Rorschach's grappling hook ("slightly unphysical, but not egregiously so").

The Phenomenon: The Comic That Changed Comics (27 minutes) is a reverent backgrounder on the comicbook Watchmen, described variously as "the Citizen Kane of graphic novels", "a new kind of masterpiece" and "a tsunami." The talking heads include not just the odd cast member from the film, but also – impressively – executives past and present from DC Comics, as well as Watchmen illustrator Gibbons and colourist John Higgins, all of whom discuss precisely what made the "postmodernist comic" so groundbreaking and influential. The only absence here (and, indeed, from all the extras) is the comic's author Alan Moore, who famously dissociates himself from all film adaptations of his work.

Real Superheroes: Real Vigilantes (25 minutes) explores the ethics and practise of vigilantism both in the world of the graphic novel (carefully contextualised within the social milieu of the time when it was written), and in real life. It includes fascinating testimonies from members of the Guardian Angels, a court expert in the use of deadly force ("there's a romanticism to vigilantism in Hollywood, but there is absolutely nothing romantic about an autopsy"), and a pair of self-appointed - and clearly unhinged - masked vigilantes ("it's time to take action, that's what we have to do"). The contradiction in Rorschach's overt psychosis and his popularity as a character is discussed, and professor of American history Dr Thomas Spencer concludes, "vigilantism seldom turns out well" - a principle borne out by the film.

This excellent package is rounded off by options for audio description and subtitles for the hard of hearing, and a three-minute mock-up 1970 NBC Night News Report on "Ten years of Doc Manahttan". Only the music video for My Chemical Romance's Desolation Row is disposable.