While it is true that the Garnett translations are "dated", and in some cases inaccurate, I find that she has preserved the voices of the Dostoevsky's characters in an authentic way, using a register of Victorian English that quite well renders the social structures of 19th century Russia. Of course, any judgement as to "authenticity" is going to be subjective; nevertheless, having recently read both 'Idiot' and 'Brothers Karamazov' aloud (to my girlfriend), I can say that Garnett's Dostoevsky translations are a pleasure to read.