This info is from the Pulp Gamer site:
Stonehenge is in one box with one set of pieces but with five unique set of rules designed by five game designers. These include an Arthurian showdown by Richard Borg, a monumental fire sale by James Ernest, a druidic election by Bruno Faidutti, a magical convocation by Richard Garfield, and an alien chariot race by Mike Selinker.
Here is the web site of the game with additional info.
One game board and five ways to play, with expansions on the way and all for $50.00.