subpar to my expectations, I think I bought this game(apart from the super awesome cover art) to get to know the world of warhammer 40k more, I visited Gameworkshop and played a WH40k game on my n-gage, and so I was kinda hoping this game would make me familiar with the universe. an example of a game which did just that splendidly was the Game of Thrones game, I've never watched the series, the game had both great gameplay and twist but also delved into the GOT world details so heavily I didn't follow much, but enough to get a feel for it, to become familiar with it. there was a lot of story there.
in Space Marine the gameplay design is mediocre, it's fun and great, but you've had the same experience in a gaziliion games before, and there isn't any new experience. very liniear, too simplistic level designs, and I might say the graphics are also a disappointment but that wouldn't be fair of me, since I'm playing this game in 2015. the story isn't that complicated either.
I came here wanting to get to know the world and the races and the politics and the history, was I got are enemies of different colors and weapons to kill in many many ways. fun, repetetive, not what I was looking for.
oh, and the button mapping is the worst I can think of in recent memory.
and one last thing, i realized later on that the game has huge structures and beatuiful environements. however they're all up such that they don't appear in your normal view while going around, you have to stop and look up at them, if the camera was zoomed out while not in combat or centered up that might've made you enjoy the scenery more.