I’ve bought Civilization V game on steam few days ago. Downloaded and installed it, but was unable to launch because of steam_api.dll is missing error. Reinstallation of the game didn’t fix the problem. My friend told me he had the same problem in Resident Evil 6 game. We started to search for the solution on the Internet. We found that a lot of people having same issues with steam_api.dll is missing errors in Civilization 5, Resident Evil 6 and 7 Ways to Die. It looks like it’s a common error for those games in Steam. However, we have discovered a quick and easy solution how to fix steam_api.dll is missing error.
We found that steam_api.dll is a system library of Steam Client API. It was developed by well-known Valve Corporation. Most of the times, steam_api.dll is missing errors happening because your steam_api.dll was corrupted or deleted. To be able to launch games on Steam without getting steam_api.dll is missing error you will need to download and install this file from here: http://fix4dll.com/steam_api_dll
If it didn’t work for you then you might try copying that file into your steam game folder (C:\Program Files (x86)\Steam\SteamApps\common\GAMENAME\).
This should solve your problems and you can now play your games.