Much as I like conspiratorial and paranoid cinema, this never managed to convince me of its credentials. Sure, Carrey plays a dog-catcher who gradually becomes convinced, through a mysterious book which seems largely based on his life, the number 23 is central to everything. However, it's probably not giving too much away to say that this interesting concept is, in fact, irrelevant to the final conclusion. Yet, for what is basically a very large red herring, the script sure spends a lot of time going into the whole #23 thing, and depends too much on coincidence and contrivance, on a quite convoluted level. It's difficult to say much more without serious spoilers, yet let's just contrast something like Memento which, while unquestionably contrived, set out the rules early on and then stuck to them, even if it caused other problems. Carrey is significantly more restrained, easing back on the zany humour which made him (for some reason, personally unfathomable) a star. That is a relief, yet he is never convincing when playing his literary alter-ego Fingerling, who is far more hard-boiled and film noir than the actor could possibly be.
Some stuff does work, most notably early on, with Schumacher getting a good handle on the unsettling feel - say what you like about the director [and "he's uneven" would be fair comment], he certainly is not afraid to turn his hand to different genres. His last three films have been this, Phantom of the Opera and Veronica Guerin. Madsen fares somewhat better than Carrey, also playing a double-role as his character's wife and the femme fatale with whom Fingerling has a strange relationship. However, the two parts of the film never really mesh, and if you don't spot the "big twist" coming before it's revealed, you will likely find yourself with a feeling of dissatisfaction, which can be summed up as, "That's it?". Conspiracy cinema is a difficult genre to pull off effectively; while it's not so hard to dig the pit of madness, finding an acceptable way to haul yourself and your characters out seems to be a good bit more difficult.