Dostoyevsky is genius. I hooked up on his "Crime and punishment" mainly because I found myself similar to main character Raskolnikov
Dostoyevsky creates amazingly deep, realistic psychological portrets, scenes. He is very good at portraying realistic internal reasons WHY character behave in one or other way. He reflects human thoughts and doubt on god, morality, faith, honesty, self-punishment and so on.
brothers karamazov - masterpeace
idiot - double masterpeace
notes from the underground - great existencial novel. Constant internal monologue. Kafka loved it. (it's first and probably the greatest existencial novel)
don't be afraid of size of his books. They are not 'difficult' to read. They become difficult once you start analysing it
some of his characters I'll remember all my life as I had known them personaly..
ps. he's very good at showing people madness (gradual or sudden), self-punishment ('internal God' in his words)
pps. his books has definite structure. i.e. half book is usualy 'buildup' for smthng then it happens and the rest half is 'afteraction' and consequences.