I really wish I had such high praise for the single player portion, but it is, quite simply, a mess. It's boring, disjointed and lacks some key sense of context. Even graphically it has some failings. Normally the game is quite gorgeous with detailed textures, but be sure to make space to install the HD textures. There is some amazing use of lighting, especially in the transition from areas of varying degrees of light and dark, but all too frequently I'd hit a spot where the frame rate would slow down or lock up momentarily, often when transitioning from one state to another or when the game was spawning in enemies. It's worth noting that I never encountered these issues during multiplayer. The game also annoyingly tries to emulate the gritty realism of a dirty camera lens almost the whole time, even when it's completely not appropriate. Are the protagonist's eyeballs dirty because he's not wearing goggles or something?
The singleplayer campaign begins in medias res with Sgt. Blackburn jumping onto a moving train to stop a group of terrorists. The timeline then rewinds as Blackburn retells the events of each mission to a series of investigators. Without spoiling much, it's all supposed to lead up to this big reveal of why Blackburn is in custody, but while the idea of that moment is sound and interesting, the execution leaves it really unjustified and wondering if there were other solutions. It also doesn't help that there is little to no characterization, you just don't care about any of these people. Only one of your squad members has anything approaching a memorable personality, and the game makes it even harder to connect with these characters by constantly switching your focus. Even worse, there are at least two occasions where the game is actively trying to elicit some emotion response from you by killing off characters, but you've sometimes only known or played as that person for that mission. The minute or two before the action starts is not enough to give you any kind of context or connection to them, so the suggested drama ends up feeling really flat and gimmicky.
However the gameplay does remain strong for the most part, with the sections themselves feeling well-crafted, if maybe a little generic. Some highlights include scrambling for cover along a bridge as a plane makes strafing runs against you and retracing your steps at night through the previous level after it's been restructured by an earthquake. A few other issues bring it down though. Sometimes at night or at long ranges enemies can be a little too hard to spot, sure it's realistic, but not when the enemy and your allies all have perfect laser vision regardless. I would often be waiting to see where I was getting fired at from before being able to respond. The game also makes liberal use of some rather boring or ridiculous quick-time-events, which feels like a complete divorce from what it does so very well in multiplayer. Taking my control away and forcing me to correctly match a button to kill a rat to avoid my own death is neither fun nor exciting.
Bottom line: Battlefield 3's multiplayer continues to excel at providing a FPS experience beyond just shooting each other with handguns. The single-player barely holds up.
Recommendation: Buy it for the multiplayer or skip it if you are just looking for singleplayer.
This review is based on the 360 version of the game.