I actually liked this game.
It should be noted that I played this with a friend co-op the entire time. I never tried playing solo.
Playing with a friend was a really fun time. The mechanics were what you'd expect from a Wolfenstein game. They didn't bring much new stuff to the table, but the gameplay in general is the brutal shooter with some stealth options.
The main story is your over the top (in a good way) Wolfenstein story, but this time with BJ's twin daughters. The main story is quick, but you'll need to hit some side quests to level up enough to tackle the three middle missions.
We enjoyed the side quests, but they do use the same five or six levels, so there is level of repetition with them. But we still did most of them so we could continue leveling up our weapons and abilities to play around with different game play.
So over all, this was a fun game to play with a person. I can't speak to how it'd be without one though. I imagine I'd be a miss if it's played single player.