Level-5 has confirmed that that Professor Layton series has passed the 12 million unit shipment mark worldwide.
The first game, Professor Layton and the Curious Village, still seems to be chugging along strong, having hit the 1 million shipment mark in Japan at the end of April despite numerous sequels having appeared since its 2007 debut on DS.
Level 5 has already confirmed that a sixth Professor Layton game is in the works, , although only three have so far made it to UK shores. The fourth game, Professor Layton and the Specter's Flute on DS and fifth game, Professor Layton and the Mask of Miracle on 3DS, are still only out in Japan with no confirmed release for the West.
Being a text-heavy, story-based puzzle game, we don't suggest you jump the gun and import. Unless you read Japanese symbols, that is.