Let’s say a middle-aged librarian/writer had never played a video game. This person loves stories, language, and history and is not comfortable with graphic depictions of violence. This person would like to be immersed in a story that is also a game, and would prefer not to buy a whole bunch of stuff or acquire an entirely new skillset.
What’s the one game you would recommend?
@Julie the thing that immediately comes to mind for me would be To The Moon. if you like that, perhaps its sequel, Finding Paradise.

these games are inexpensive (especially if you get them on sale on Steam, before the 5th), will run on nearly any personal computer, and don't require significant "gaming" skill (something that gamer-types have criticized it for, as "lack of gameplay")

i would warn that they do deal with some complex issues including mental health topics and end-of-life care, as a core focus of the story. and if you're susceptible to crying through a sad story, this one
will have you in tears.

i can think of a few others, but not that i would recommend more strongly than this based on your criteria. this one sits at the top of the list of "story-games" that left an emotional impact on me, and should be reasonably accessible to a non-gamer.
@Julie in addition to To The Moon, i see others recommending Gone Home, The Stanley Parable, Grim Fandango, and the Monkey Island games, and i would second all of those as well - and i could come up with a few more that would probably fit - but i'd still place To The Moon above all of those based on what you said (and, honestly, just in general)