Most widely spoken fictional language

Although it is impossible to know the number of speakers, there is little doubt that the Klingon language, invented for the Star Trek films by linguist Mark Okrand (USA), is the most widely used language of its kind. Participants at Star Trek conventions frequently converse in the language and in addition to a Klingon Dictionary there are Klingon translations of Hamlet, Much Ado About Nothing and Gilgamesh.  Amazon.com lists at least five other books written in Klingon or containing large tracts of the language, and the Google search engine is also available in Klingon.