We're not talking Shakespeare or Chaucer--or Dickens or Scott, or even Barrie. We're talking William Hope Hodgson. All of the above-mentioned have been "adapted," "condensed," and "simpified" to a faretheewell in a number of media, including prose meant for adults. If you want to make him more accessible by taking the gingerbread off his language and the padding off his narrative, I see no moral or legal reason why you shouldn't. But I wouldn't call it a "translation" (which it isn't). I'd call it an "adaptation."