"Winter Soldier" proved everyone wrong. It redefined Captain America for a new century, pushing him into the realms of political thriller. Cap's history is slightly tweaked, with a cosmic cube bringing new memories of Steve Rogers' time in the 1940s to the forefront. The most important of which is Bucky's origin: he wasn't just some kid who stumbled into an unmasked Steve's tent: he was older, and entered training for black ops work after his discovery. After teaming with Cap for some time, Bucky was seemingly killed in an explosion.
Here, Brubaker crafts a scenario in which Barnes didn't die and was instead discovered by a Russian patrol. He gets a new arm and is brainwashed into becoming an assassin, a job he shows extreme aptitude for. However, his mental state forces his controllers to put him into deep freeze, thawing him when necessary. As a result, Bucky emerges in this story only slightly younger than Cap.
What I really like about "Winter Soldier," and what makes me understand why Marvel has been quick to promote that the Winter Soldier is Bucky ahead of the film, is that the return of Cap's comrade isn't treated as a stunt. The revelation is not handled with very much weight - what's important is how Steve reacts to it. His reservations about fighting his friend, let alone accepting the truth, make up the meat of the narrative, which really sets this apart from most comic book "surprises." It's aided somewhat by the thought from the reader that it couldn't possibly be Bucky. Again: he was "Ben Parker Dead."
This incredibly important event is only part of a tapestry. Brubaker weaves in characters from Captain America's past seamlessly, including the likes of Sharon Carter, Nick Fury, Falcon, Crossbones and Jack Monroe. The Red Skull also appears sporadically, but when he does it is huge.
The real star, though, may be new character Aleksander Lukin who ends up in possession of the previously-mentioned cosmic cube. The corporate giant is a complicated adversary for Cap, who can't just swoop in and punch the guy. He finds that out the hard way. Worse, he's even more dangerous and unbalanced than what could have been predicted. The way he uses the cube to orchestrate a major coup is jaw-dropping in its cold execution.
Overall, this makes for the perfect collection for fans of the Captain America films who want to get into the source material. Brubaker crafts a deep, complicated, reinvented world for Steve Rogers... and he's just getting started.