Oh my god, This is the worst single player mode i have ever played.
Once i got that out i can continue the review.
The multiplayer simply rocks, OMG, After you'll try it once, You'll come back to it again and again, It is so addicting. When i first saw pictures of the game before it came out, it looked kinda creepy and bad, It surprised me, Really, The flow of the game is just amazing, The realistic graphics are stunning, It's shocking each and every time i see it, The battles feel chaotic, I cannot even describe it in words, You'll have to try it for yourself.
In the multiplayer you start as a privet, And have very little choice, After a while you gain experience, There are totally 55 levels and will take you 20-30 hours to reach level 55, In the process of leveling you'll get new weapons and perks, You have different multiplayer modes to attach to your mood, You'll love every single second of it, Trust me.
But if the game was perfect I would have given it a 10... but it isn't, The multiplayer has some bugs, And they can be annoying as hell, Like spawning in the enemy base and basically spawning and dying immediately because the computer has spawn you in the line of fire, The game needs a little bit fine tuning, nothing that cannot be fixed by a patch or two.
To sum up, Buy the game, Install the game, Skip single-player, Have fun.
(P.S. the single-player is only good to give you a background about the maps you are playing in the multiplayer, enjoy)