Zodiac is a meta-thriller: it comments on itself and other serial killer movies, and in a broader sense, on our obsession with real life and fictional serial killers – especially the unsolved cases, from Jack the Ripper on, that we keep picking at, without resolution. The movie's spiraling structure, and what to some will seem excessive length and detail, are intrinsic to this self-examining quality. I think it’s smashing – the best big commercial film I’ve seen since The Departed.

The three lead performances are excellent: Jake Gyllenhaal as the nerdy-obsessive editorial cartoonist Robert Graysmith, on whose books the film is based; Mark Ruffalo as the San Francisco police detective who worked the Zodiac case for many years; and, most entertainingly, Robert Downey Jr. as the maverick reporter Paul Avery. The widescreen images, shot in high-definition video, are often startlingly clear, and they have been masterfully edited. Director David Fincher is a master technician, and possibly not a very nice man. It’s the perfect combination for this material.

The three murders recreated in the movie are horrific to watch, but far from exploitative, and they all occur early on. The investigation, and the obsessions it engenders, are the real subject. Although the film posits a plausible theory and suspect for the Zodiac killings, it remains deliberately foggy, ambiguous, unresolved. This may well leave many viewers dissatisfied. But it is one reason why this is no ordinary thriller.

The tone deftly mixes engrossing suspense with sly humor, notably in scenes that could be read as tributes to, or affectionate parodies of, paranoia classics of the '70s (All the President's Men, The Parallax View, The Conversation, the our-daddy-is-an-obsessed-weirdo scenes in Close Encounters of the Third Kind). The production design, without calling undue attention to itself, quite brilliantly recreates the 1969-1978 era - or possibly a more accurate way of putting it would be that the look of the film captures our own changing attitudes toward the styles of those years. The soundtrack makes very potent use of period songs as well (I always loved Donovan's slightly creepy "Hurdy Gurdy Man," but after seeing this movie you may never be able to hear it again without shuddering). I’ve seen the movie twice now, and I was surprised that the 155-plus minutes flew by the second time. Fincher is a warped wizard of cinema, a gifted storyteller who can twist a viewer's perspectives and perceptions and leave you wanting more.

I had my own experience with serial-killer obsessiondom, involving Jack the Ripper. I became fascinated by the case and bought several books, determined to come to my own conclusions. But at some point I began to see the truth: from this distance, with the evidence long fading, there are many, many suspects, and convincing reasons to consider nearly every one "likely." And none will ever be conclusively proved or disproved. I tossed the books aside, half read. Yet the unanswered mystery still gnaws at me. This tantalizing, exasperating mood of discovery and frustration is what Fincher’s movie is all about.