Over the last 40 years, I've bought a lot of RPGs & supplements; none has triggered near instant regret the way this one has.
I like exchanging letters with friends, and I like writing up my group's Call of Cthulhu sessions; it sounds like this game ought to be my kind of thing! However, I can't tell, because I can't handle the rulebook.
Bottom of page 10: "It's also time for you to learn what De Profundis is all about." OK! Great! I was hoping to find that on page 1 or 2, but good, let's go!
Page 14: "But for now it's more important to explain the game's concept, as well as its details and my own thoughts about it, as precisely as possible." OK! That's what I've been waiting for!
Page 15: "Ah! The play report from your last session of Call of Cthulhu was excellent. You got me all but carried off to Damian's room and sitting there with you, then off with the group into the depths of the ocean in that small bathysphere. Top quality CoC !" None of that means anything to me, and after pages & pages of this, I'm now too frustrated to care whether there's a game hidden in here. Dude, I'm out.