I always loved books where the author hides important clues and you really have to read every word to find out who did "it", who the enemy is or whatever.
I love it when the author mentions something in a subordinate clause and it's actually the key in the end. It doesn't have to be a detective or crime book (:
And please no typical murder cases, I don't really enjoy them though I love good psycho thrillers
by DontmindmeIoI