4)He Who Whispers by John Dickson Carr
This one, unlike the other three, is pretty hard to solve. It has a very creepy supernatural atmosphere and offers impossible crime after impossible crime, eventually asking the main character(and the reader) whether the culprit is supernatural or not. It's basically what Umineko tried to be, but much better. This is a novel I'd recommend for beginners because even if they "lose" they'll have an amazing experience and they'll be motivated to try harder next time to solve the puzzle.
Heh. Was gonna hijack the title to ask you what the one book you recommended where it presents the possibility the culprit was supernatural. And now I don't have to.
--
"Oh God, maplejet's trying to be cool again. I'll call the ambulance." - Wylvane
[NO BARKLEY NO PEACE]