I'm a big fan of the Baldur's Gate series. They're very old, but they've produced an enhanced edition available on Steam that's compatible with modern engines.

The games are RPG strategy. Combat is real-time but pausable. Setting is Dungeons and Dragons Forgotten realms with most of the familiar aspects from the game (it is based on 2nd edition though so some elements are likely to be less familiar, biggest mechanical difference is that low AC is good and instead of Attack Modifiers they use THACO (an abreviation for To hit Armor Class 0. This is why low AC is better, since your armor class is added to the enemy's THACO, making it easier for them to hit you unless it's negative)

Anyway, the system is less of the appeal compared to the actual story. Lots of interesting and memorably characters, especially in the sequel, where they traded the sheer number of NPC companions to enhance those the stories behind those that are in the game.

Of course if you really want to go down the amazing story route, I'd recommend Planescape Torment, which also got an enhanced edition recently, and which is commonly praised for having one of the best stories in RPG history.

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Alternatively, I recently picked up a neat game on steam on the cheap. Steamworld Heist. It's a turn based third-person shooter strategy game like X-com, with the primary difference being that it's also a 2D side-scroller. This means that the fundamental mechanic is that you have to manually aim your shots to get through cover, often by doing cool ricochet trick shots which makes for some satisfying game play.

I understand the reservations about shooters, but it may assuage your mother since the setting is all steam powered robots. Thus there's no blood, and they go for more goofy steampunk weapons than anything realistic. So you just shoot at foes with your snazzy brass gear-covered pistol and they fall apart into a bunch of scraps, not terribly violent. (They even mention in-universe that most of the robots can easily be rebuilt, as this is what happens when your own party members are defeated.)

The story's pretty basic but it serves its purpose for carrying the interesting game-play and is helped by its amusing cartoony steampunk space aesthetic. It's also got some replayability despite the fixed storyline thanks to variable difficulties, a new game plus mode and a couple of cheap DLC missions they put out. Well worth the five dollars I paid for it on sale.