It's really nice, WH40K style.
If you are not familiar with the setting, think deep space Aliens (like the movie), just more badass (see the screenshot).
It's nothing like the vague afterthought Hunters 2 was.
Actually the game is all 'story'...there aren't random missions.
It's 40 mission campaign, very tight with spoken dialogues (chatter between marines, it's really cool...Baldur's Gate banter style) in every mission (but the prologue maybe, can't remember).
It's divided in chapters, consisting in 4 missions tied together (same 'place', all maps tied, auto conclusive mini story/mission).
Being WH40K don't expect a JRPG with insights on motivations of Maries or things like that
Their only purpose is wiping off the universe the Xenos, so the missions (which are very varied) reflect that (destroy this ship, nuke that planet, steal their plans, etc...).
Last chapter is awesome, but every chapter is better than the previous one, and they start strong already (I'm sure there will be video around the net very soon, just saw one on TA....too bad the author didn't even realize you can pitch the camera!!! I always play in iso, it's so cool).