It is legal but in any case why do you care. If it were illegal it’s not something that would be enforceable or something they’d be likely to “catch” you for, and it’s definitely not unethical. Everyone should be free to do whatever they want with published literature.
If you see a game you think you’d enjoy, go for it.
Personally I find that I’m not super into video games as an adult just because I don’t have the time, and I don’t find them very fun in short bursts. And when I do have the time I always think to myself I’d be better off spending it on a “productive” hobby like programming. That’s an entirely personal thing for me, but it may be something you want to consider, ie if you want to learn a hobby that’s also considered a real world skill so to speak, and one that could give you products of your hobby you can actually use and enjoy (eg programming, crochet, cooking, woodworking, etc—so creative hobbies).
Also, feel free to pirate a game if you don’t know if it’s worth the investment, especially since you won’t have a reference point of games you do enjoy. I have no ethical quandary with pirating any game, but if you do, you can just buy the game if you like it, and that way you won’t waste money on a game you only get 5% of the way through before getting bored.