Steam Will Not Open Amnesia: A Machine For Pigs
Solution 1:
Based on complaints on the steam community forum the game is currently broken for a number of people.
However, the asker was able to solve the problem by downloading a .dll file here. Apparently steam is not downloading .dlls appropriately on some x64 systems
Solution 2:
I don't know if you've tried this or not, but it worked for me! In your Machine For Pigs folder, delete the three following files; xinput1_3.dll, msvcr100.dll and msvcp100.dll. They aren't actually needed for the game, but they cause this issue. =)