L.A. Noire is ostensibly a game. But it's not.
Yes, it contains games. Some where you move around an environment manipulating objects. Some where you virtually interrogate various characters. Some where you drive cars, or chase criminals, or shoot at them. Or read ledgers or (shudder) balance on a plank. Individually these range from fun to downright annoying.
But it's not a game.
L.A. Noire is, essentially, an interactive episodic TV series. It has a defined beginning, end, and plot arc. It has named, fixed episodes (aka cases) and series (aka desks). All you can control, really, is the specific flow of events and the tone of the outcome of any given episode.
I suspect it's this not-gameness that accounts for the hot-and-cold opinions of the gaming community. It doesn't really fit in the boxes we're used to. It's sort of an adventure game, except you can't really fail, and the puzzles aren't hard. It's sort of an open world game, except the open world aspects are largely superfluous. The character you play doesn't grow in power as the game progresses. You're put in situations where the “win” situation is charging a specific person with a crime -- when both you and the protagonist know that the person probably didn’t do it . You make choices along the way, but they aren’t the good/bad style branching choices that have come to stand for “choice” in a games. And, while avoiding spoilers, the plot take several turns that are atypical for a videogame.
Despite all this, I realized I loved this "game" -- hence the five stars. I eagerly looked forward to playing it every evening, and finished it faster than just about anything I've played in a long time (both Dragon Age II and Portal II sit unfinished on my PC).
When everything worked, I felt like I could inhabit the character in the story. Yes, finding clues was generally easy -- because Phelps is a crack investigator! And combat and chasing down crooks was easy -- because Phelps was a marine! I even loved the fact that the interrogations were often frustrating -- because in real life, or at least the dark "real life" that is presented in noir, figuring people out is hard. They don't always make sense.
Ultimately, before dropping $70 on this game, I'd ask myself one question: “Did I enjoy Chinatown?”
If the answer is yes, you'll probably enjoy L.A. Noire. If the answer is no, I'd stay clear. And if the answer is "what's Chinatown?", you have some homework to do first.