When Watchmen, Alan Moore and Dave Gibbons’s acclaimed comic, completed its 12-issue run in 1987, it changed the way we look at superheroes. At its heart, the book could be called a murder mystery set in a world of costumed heroes, but Moore’s razor-sharp writing and Gibbon’s simple but expressive art managed to roll in commentary on every major genre of comic book since the golden age, as well as some very dark, very serious observations about human nature. Horror comics, romance comics, pornographic comics, pirate comics and, of course, superhero comics were all subject to merciless deconstruction at the hands of two mammoth storytelling talents who would later become two of the most important names in the industry. Due to the comic’s reliance on the history of the medium (not to mention its incredible density), many people have called the book “unfilmable” — Moore being among the most vocal of them. And while the idiosyncrasies of the source material do create some problems in Zack Snyder’s (300, Dawn of the Dead) adaptation, they don’t prevent him from culling a solid, extremely entertaining superhero movie from the editorial quagmire.

The plot, much of the dialogue and most of the larger themes are very faithful to Moore and Gibbons’s book. Set in an alternate-history 1985 in which Richard Nixon has been elected to his third term as president, the U.S. and U.S.S.R. stand on the brink of nuclear war and costumed heroes — where once they were endorsed by the government — have since been outlawed, the only thing standing between humanity and annihilation is Dr. Manhattan (Billy Crudup), a big, blue übermensch with godlike powers. Against this backdrop, a costumed hero cum government agent named The Comedian (Jeffrey Dean Morgan) is thrown off a high building, and Rorschach (Jackie Earle Haley) — the only vigilante who refused to retire — sets out to investigate. Along the way, he uncovers many of his old friends’ secrets, as well as a vast conspiracy that may implicate all of them.

In the broad strokes, Snyder’s adaptation gets far more right than wrong. The new ending works, the complex, multi-protagonist narrative manages to be both comprehensible and compelling, and the action is both slick and brutal — suggesting something of the darker, fetishistic layer to the “costumed hero” lifestyle that’s implied throughout Moore’s story. Where Watchmen fumbles is in the more delicate moments. A poignant monologue by Dr. Manhattan where he laments his estrangement from humanity while reflecting on all the people he’s hurt is reduced to a couple of minutes and a handful of scattered motifs. What was once a touching connection between two of the heroes, forged from fear, confusion and puppy-dog affection, is reduced to a hilariously crass slow-mo sex scene set to Leonard Cohen’s “Hallelujah.” Worse, at one point, one character asks another with the utmost sincerity: “What happened to us? What happened to the American Dream?” In its worst scenes, Watchmen verges awfully close to self-parody, but in its best, it’s a pitch-perfect replication of one of the best comic books ever written.

In a way, Zack Snyder’s Watchmen is equal parts faithful tribute and competent adaptation — much of this owing to the fact that he opted to transcribe the book to the screen rather than modify it to fit its new parameters. In the necessary brevity of this approach, the film chops out or glosses over many of the comic book’s intricacies — and as a result, much of its genius — but even with its shortcomings, it remains eminently watchable.