You can find links to all supported platforms, including PlayStation 4 and Xbox One, on the official 2K Mafia website . Why Official Sources are Better: Security: No risk of viruses or "hidden" installers.
Your progress is backed up so you don't lose your data.
One-click install—no need to worry about missing .rar parts.
You can purchase and download it directly from the Mafia: Definitive Edition Steam page .