I want to play that so bad right now. The cat like movement with wall-climb, plus the alien vision is easily one of my top 5 unique gaming experiences.
During what I still consider the golden age of gaming, which is 1997-2004, most single player games were aiming for 30-35 hours. That has been my sweet spot ever since but it doesn't mean a game can't be satisfying with less than that.
I personally don't find anything shorter than 10 hours enough of an experience. 25-30 sounds very reasonable.