The simplest way to describe Omerta is that it's a dumbed-down version of Tropico moved to the Prohibition Era, made by the team that bought the rights to start developing those games (starting with Tropico 3).
If you've never played or heard of Tropico, though, that's not going to help you much. So the next simplest explanation is that it's a turn-based Mafia-themed strategy game in which the main thrust is taking over businesses in 1920s Atlantic City to keep your income flowing and grow your criminal empire. You'll use the talents of a squad of goons that you recruit, and often this involves combat, which resembles a cross between X-Com and Fallout. There's also a Fallout-like aspect of selecting new perks for your goons as they level up.
So, unique turn-based Mafia setting with classic Fallout-style combat and leveling? How could THAT go wrong? Well, two problems -- the actual strategy portion of the game is almost entirely lacking in challenge or complexity, and the combat turns out to be kind of a clunky and simplistic mess too.
You take on Atlantic City in small and isolated chunks, each with a specific objective to accomplish like driving some competing racketeers out of business or setting up a network of speakeasies. While I personally usually like smaller maps in my strategy games, here it just fosters repetitive patterns and a general lack of challenge. Each map is pretty much just paying off a series of informants to uncover the different buildings, then setting up your money-making operations (interspersed with a few plot-related hiccups like getting jumped by an enemy squad out of nowhere). There's a wide range of different businesses, but the brewery-speakeasy combo you lay as your foundation in each map usually ends up pumping you with so much money that the other business types become irrelevant. This portion of the game is also a little tedious, as you have to wait for your troops to roam to and from their tasks without the nicety of a progress bar, and there's nothing to do but twiddle your thumbs when they're all busy.
Still, the strategy element isn't *bad*, just a little more toward Mafia Wars than toward Sim City than most PC gamers would probably prefer. The combat is actually the real disappointment. It employs a simple cover system similar to Jagged Alliance, where characters will automatically use walls and tables and stuff if you park them next to them at the end of their turn. It ends up being window dressing only, however, as the extremely simplistic computer AI just charges you like a suicide drone in every battle. This also takes away from the build potential of perks, since there's nothing to contend with but dudes who run right next to the nearest guy and fire a shotgun in their mouth.
The best bits of the game are actually the soundtrack, a really great mix of era-appropriate jazz and traditional Jewish music, and the surprising diversity of the opponents you face. You'll get the full spectrum of even the minor criminal players who were vying for control in the days before the Sicilians became America's Top Goons, including Jewish and Irish gangs and the Ku Klux Klan (who hate all immigrants in this one, including the white ones).
Omerta might be good if you want a rock-simple strategy game or are just really keen on the idea of Mafia strategy. PC just seems to be the wrong format for it, though. It came out in 2013, so it could have been released on mobile instead, and it really seems more pitched for the casual audience.