Is it just reprint or are there entirely different cards? Can not find any Arkham edition boxes on the intrawebs for sale.

I guess you're talking about Arkham Edition and Eldritch Edition of the CCG game?

If yes, so they are completely different series of cards.

If you are talking about the coming expansion "Secret of Arkham" for the LCG game, so it seems that is is partly reprints of CCG cards (but not sure at all if they are only coming from the Arkham Edition cards set) and partly a few new cards.