We recently had a number of issues with getting Football Manager 2015 to run after downloading the game through Steam. Whenever it tried to update just before starting the game, Steam would pop up an error stating Incomplete Installation Error 55.
Bit frustrating considering we paid £30 for a game we cannot now play!
However, a quick fix is available, all you need to do is run the following command (assuming this is where you have Steam installed):
C:\Program Files (x86)\Steam\bin\Steamservice.exe /Install
You must ensure that Steam is fully closed before doing this and for good measure, might be worth running it from an elevated command prompt.
After doing this, Football Manager 2015 run with out any issues at all.
The problem apparently is to do with Anti-Virus programs stopping the steamservice.exe from fully installing.