Ever since I played Red Dead Redemption and saw the trailer for L.A. Noire, I am very excited for it, and predicting it will be a great game. Fortunately, the game is awesome to play, in my opinion.
Storyline
This game is a combination of action and open-world genres. The main objectives in every cases is to find evidences and clues to solve cases. However, finding clues or evidences are not as easy it sounds.
In every crime scenes, you need to find evidences and clues to find and convict the suspect in the particular case. To find evidences, walk over to any suspicious objects around to examine it. With the default setting, you can feel a vibration whenever you are near to a clue. However, not all clues are relevant to the case, so you need to see carefully which clues are important in order to solve the case.
The game has a level up system. By gaining enough experience, you can get Intuition Points. Intuition Points allow you to do three things. One, to discover all important clues in your map. Secondly, it allows you to ask the online community on how to solve this case. Thirdly, it allows you to eliminate an answer during interrogations.
Storyline

Cole Phelps rise through the ranks in LAPD quickly due to his amazing investigative skills.
The game takes place during 1940s to 1950s at Los Angeles. Cole Phelps was a hero during the war, and joined LAPD later on. He solved a lot of cases with his great investigation skills, and allows him to get promoted fast in LAPD ranks.
The game have 21 main cases, with several arcs. You will control Cole and solve cases as he climbs upwards in LAPD ranks in various departments, like Patrol, Traffic, Homicide, etc. Also, during the period Cole works in certain department, all cases involved are linked closely, whereas there are some cases are standalone cases when playing early in the game.
Each character have their own development that can be seen within the game's great cutscenes and voice actors' performance. You can see how the character reacts to something realistically, thanks to the great Motion Scan technology.
The game's storyline is nothing short but amazing. Thanks to the superb acting by the voice actors', they deliver convincing performance that makes the game's storyline as realistic and believable as possible. The story is full of suspense, mystery, drama, and etc. It's not everyday you find great stories in a game.
Gameplay

The game plays like most open world games like Red Dead Redemption, Grand Theft Auto, and etc. However, investigation is the main gameplay element in this game.
This game is a combination of action and open-world genres. The main objectives in every cases is to find evidences and clues to solve cases. However, finding clues or evidences are not as easy it sounds.
In every crime scenes, you need to find evidences and clues to find and convict the suspect in the particular case. To find evidences, walk over to any suspicious objects around to examine it. With the default setting, you can feel a vibration whenever you are near to a clue. However, not all clues are relevant to the case, so you need to see carefully which clues are important in order to solve the case.

You can use Intuition Points to find clues easier.
The game has a level up system. By gaining enough experience, you can get Intuition Points. Intuition Points allow you to do three things. One, to discover all important clues in your map. Secondly, it allows you to ask the online community on how to solve this case. Thirdly, it allows you to eliminate an answer during interrogations.

You have three options during an interrogation. First, you can deduce the person is telling the truth. Next, you can doubt that person's statement. Finally, you can accuse the person lying with using an evidence to back it up.
Interrogations in this game are very interesting. You have to ask some questions from witnesses and suspects in order to get evidence as to who is the real suspect is. During a question, there will be three options, which are Truth, Doubt, and Lie. These three options will help you to find the real suspect. However, two of the answers might be wrong whereas the remaining one is the correct one. To find out on whether the person is lying during a question, hiding something, or telling the truth, you have to see the person's expression and decipher whether he is telling the truth, or not.
Using Intuition Points allow you to narrow down the 3 answers to 2, which can be helpful in some tough cases. However, if you are unable to get a question correct, the path of finding new clues or suspects will be harder. That is why, finding clues at crime scenes or suspicious places are vital in the interrogation sessions, as you need the correct evidences to proof that person is lying.

It takes practices to know whether the person is lying or not.
If you want to know on how the person is lying or not, take a look at his expressions. If he is looking at you straight in the eye, usually that person is telling the truth. If he stammers while giving an answer, he might be lying, or hiding something from the police.
Before accusing someone of lying, have a look at your notebook as to whether you have the evidence to back it up. Your notebook contains all information of the evidences and clues found during a case.

The game has it's own set of action pieces.
To prevent the game itself from being boring, it has it's own some action sequences. There are times where you have to fight bad guys in a case, chasing someone on the wheel or on foot, tailing someone, etc. They are very cleverly implemented in the game, giving unpredictable nature for each cases.
The game's shooting mechanics are similar to Red Dead Redemption's shooting mechanics, which is third person shooter. You can pick up weapons dropped by your enemies and use them to your advantage.
The game's exploration takes the whole area of Los Angeles. You can drive cars around, or ask your partner to drive to a destination. However, you can also enjoy driving the car around before going to your next objective, solving minor crimes along the way.
I have to applaud Team Bondi and Rockstar for creating a great game with awesome gameplay system. In certain chasing sequences, you are limited to one option to stop the suspect, so it creates a minor problem to players. For example, you are unable to fire a warning shot in most chasing sequences, and you have to tackle the suspect to catch him. However, this is only a minor complaint and will not detract the great experience of playing this game.