I've played through this over the last couple of evenings, and have loved it.  It's easy to think of the game as a gimmick, with the idea of controlling two characters at once, but once you get used to this (which takes a while!) the game reveals itself as a clever puzzle platformer with moving story.

The puzzles throughout the game are varied enough to not outstay their welcome, without the need for any sort of power-up mechanic. Some of the highlights were manoeuvring a long metal pole through  a maze with limited turning points, and a long section where one brother hung from a conveyor belt while the other opened gates.  These were by no means the only clever puzzles, and even those which are pretty standard parts of videogames were freshened by the control scheme.

The story was equally innovative, in that it explored the themes of sickness and death more intimately than most other games. The game starts with the background story of the little brother witnessing (and finding himself responsible for) his mother's death, followed by the main story of his father's sickness.  The two brothers journeyed to get medicine to cure their father, emphasising the importance of the family.  The strong bonds that the story imposes are all the more effective when ... things happen ... at the end of the game.  I've rarely felt such a sense of shock and horror.

Well worth playing through, though don't expect happiness and fun all the way through.

While looking for beaver furs in the Northern regions, I noticed a new stranger mission open in Blackwater.  I met a government man who told me that Edgar Ross was living in a shack overlooking a lake.  Suddenly the lack of a previous ending made sense.  Don't read if you've not played ...