so that is not Lavi? so the eyepatch was only an accessory to hide that he is not really t...

What I understood is Bookman is a title that's passed down to the next person born with a mark, if Lavi was born with it (they don't say what type of mark) that means the previous bookman jr. probably passed away. I don't think they are trying to hide his dissapearance, Lavi just took his place as the old man's disciple because there has to be two bookman so that recorded info. can get passed on. My theory is the eyepach hides the "birthmark" (if he has it on it's eye) so that other foreign bookman don't recognize him.