The error generally looks like one of these variations:
A DLL (Dynamic Link Library) is a file containing code that multiple programs can use. In this case, the DLL allows the game to communicate with Steam (for achievements, saves, and DRM verification). failed to load library steamhdll
Bleeding-edge beta features can break compatibility. Reboot after completion
A corrupted download cache can cause Steam to mismanage local files. The error generally looks like one of these variations: