The riddle with the books enraged me. But I still managed to pass. This game is great. A huge job of developers and voice actors. It sounded like they were professional announcers. It's my favorite right now.
Enraged is a worrying word :P I hope it was that kind of "fun" frustration all adventure games give. Most of the actors are professionals indeed, and those who aren't - well, they aren't yet. They sure have the talent and capabilities to :)