I mean, the books I am talking about are also published by relatively large publishers who do hire real translators. I've read other things that were translated unofficially by hobbyists, and with those you run into a much wider variety of shit. There's some stuff that's just as good as any translation I've read, and a lot of stuff that's marginally better than using Google Translate, and everything in between.

But even with the big publishers, there's still some books they don't spend as much money on, or expect to sell very well, and these are the books that will have errors and somewhat awkward language.

Still, just from reading a description of those two books and looking at them on goodreads I wouldn't see any giveaways that they are clearly a lower quality book, so I'd think you'd be fair to treat those with the same expectations as any other book.