I think the story kind of leaves you were you started. You reach no new conclusion about Bartelby. He ends up just as mysterious as he was when he stood in the doorway at the narrators office. He sheds a little light on the history of Bartelby by way of a rumor (which may or may not be true) at the end of the story.
It seems that his last job did have an effect on him. His life in this story is sort of like a 'dead letter' itself...sort of lingering with no destination or cause...
