"Inspired by the bestselling board game Arkham Horror, and set in the same eerie mythos, Eldritch Horror presents a unique, globe-spanning adventure for those intrepid souls brave enough to embark on the journey.
While fans of Arkham Horror may recognize some shared mechanics between these two sister games, these familiar mechanics take on new twists. Eldritch Horror is not an expansion, nor does it replace Arkham Horror. It is a brand new game, which stands alongside Arkham Horror and the rest of FFG’s library of Lovecraftian games, filling its own distinct niche."
(publisher blurb from FFG minisite - http://www.fantasyflightgames.com/edge_minisite_sec.asp?eidm=244&esem=1)