Impressive, Niven!
I have to say the game really surprised me, although I had to play it twice—I'm not sure if it was due to a bug (or maybe my own stupidity), but I'll comment on it here.
As a developer, you know where objects are hidden, so you think they'll be easy to find (always in the developer's mind). But when someone outside the development plays the game, it becomes much harder for them to find that object since they don't know where it could be.
This doesn't necessarily mean that I found it difficult to locate the notes at the start of the game, but here's where the "bug" (or my own idiocy, as I mentioned) comes in. After collecting almost all the notes, a new one is supposed to appear next to some rocks, but it never showed up (even though I checked the area thoroughly).
However, on my second playthrough, I found the note within seconds. So, my conclusion on that is either I was too dumb and missed it the first time, or it really had bugged out.
That small hiccup doesn't take away from the fact that the game is amazing, with a dark story and Lovecraftian horror elements (which I loved). Without any doubt, I can say this is one of your best games, Niven.
Best of luck with what's to come in the future!