What if you don't need listening or speaking skills, only reading? In your opinion is Duolingo a good fit for someone who only needs to learn to read the language?
Not the gp, but I used Duolingo quite a bit, and recently learned Spanish to an upper intermediate level. In my opinion, Duolingo is just as weak with pure reading as with spoken language. You'll learn some vocabulary and be introduced to ideas, and that's valuable, but not enough. Just like spoken, to learn to read, you have to read a bunch of stuff you can understand. I jumped straight from Duolingo to children and young adult books, and it was a difficult transition with lots of intensive looking-up-every-other-word study, but, I mean, you do that long enough, and eventually you're just reading.