There was this tv show back in the day. Herman's Head, it was called. All these characters were inside the head of this one fella named Herman, representing various aspects of his persona, and they'd fight and agree and so on and so forth.
Well, Identity is half a good movie, and then another half of a rather silly movie, whose chief virtue is to provide proof of why the characters in Herman's Head were never given guns.
And if it seems as if I'm churlishly jumping straight to putting the emphasis on this latter half because, of course, it's what you walk out of the theatre remembering: you don't remember that John Cusack was just fine, and that John Cusack being just fine = most any other actor working overtime. You don't remember that Ray Liotta and John C. McGinley were above reproach. (Of course, neither do you remember that Jake Busey played Jake Busey, AGAIN, and he was loathsome, AGAIN, and not in the way he intended, just plain get-the-fuck-off-the-stage loathsome. It works both ways like that).
So, fine, okay, we're well into spoiler territory here. Identity, as has been noted, IS The 3, fictional awful-blockbuster-writer Donald Kaufman's fictional awful-blockbuster from actual great movie adaptation.
It's also somewhat Being John Cusack, but - and there'd have to be a but, wouldn't there just? - whereas Spike Jonze makes clever movies which create a mythological universe in which hackneyed multiple-personality thriller plots seem perfectly natural, Mangold and writer Michael Cooney, well, don't.
Rather, they construct an intriguing universe, peppered with pastiches that you're more than willing to allow because it feels like they'll have the sophistication to grow into knowing Hitchcockian nods, draw you into this clever little universe, then give themselves the world's biggest, silliest out by doing something my rather poor 3rd-form English teacher would, out of simple reflex, chastise them for: the ol' "and then I woke up and it was all a dream" gambit.
Which, while the odds are stacked against it, still has a fighting chance: nobody wants to believe they've just spent an hour or so investing themselves in a totally silly movie. If Cooney can pull anything out of the hat to make us stick with it, we'll go with it.
And what's he got left in his bag of tricks? RAY LIOTTA DID IT. Oh, come on. Ray Liotta always did it. And - oh - what's this? - surprise bonus twist, stupid flashback montage, THE KID DID IT? FUCK OFF with The Kid Did It. So you've seen The Omen. Silly Identity. Tricks are for kids. Go stand in the corner - Spider, move aside, we've got company - and think very hard about what you've done and see if you can't come up with a better third act. Here, I've got a fictional script and a tv series for you to look at.