Mafia III is a contender for worst PC port of the year. The game, which is now available through Steam, is plagued with numerous issues including an unforgivable cardinal sin: a 30 frame per second cap.
While 30 FPS may be acceptable for console gamers, frame rate caps should never be implemented in PC titles. The ability to play games at 60 FPS or higher is one of the main advantages to PC gaming, any any cap just shows that the studios involved, in this case developer Hangar 13 and publisher 2K Games, don't understand the PC gaming market.
Understandably Mafia III is being slammed in Steam reviews for its 30 FPS cap, and gamers are also reporting several other issues: in game textures are blurry, there are a number of problems with the interface (especially above 1080p), and there is no support for multi-GPU systems.
A message posted on the Mafia III website acknowledges the issue, and states that "the team has been hard at work ensuring that Mafia III’s performance is consistent across all platforms, and right now the game runs at a solid 30 frames-per-second." In other words, the developer implemented a 30 FPS cap on console and didn't bother removing it for the PC version.
The good news is that a patch is being developed that will "give players the option to play Mafia III at higher framerates." 2K Games will release more details "very soon" about the update and when it will arrive. The team is also considering a number of "additional post-launch improvements on PC that would give players more control over how they can tailor the game’s experience to suit their rig’s performance."
For now, you should probably hold off purchasing Mafia III on PC until these issues are resolved.