Absolute fantastic atmosphere and story. Combat has a nice strategy side to it, despite having THE best timing element I have ever encountered. I've missed this in a game since the first Witcher game. Only for the story, the world, the characters, the atmosphere, and the music I advice you to play this game. And paying full price is actually okay for a game of this level.
I have very little positive to say about this game. Positive: WH40K Negative: The rest The story it superficial and predictive. The mechanics in the game are moderate at best. Gameplay is repetitive and boring. All in all this is a quick money grab and has nothing the to do with the two previous games from Owlcat that I love dearly.
I bought this expansion on sale after thoroughly enjoy Mechanicus, but even for the sale price, this is not worth it at all. There is no new campaign, there are some new missions and battle maps and one new skill tree. In total this amounts to roughly 15 % of extra content to the original game. This should have been an update, not an expansion! Just to give you the idea - the entire expansion is an exe file of 6 mb.