A model that I look at closely for my developing list of design elements for cross-media stories is that of ARGs (alternate reality games). There are two books on the subject and recently, an interview with ‘puppet-masters’ Elan Lee and Sean Stewart at Cultural Gutter.
Gosney, J. (2005) Beyond Reality: a Guide to Alternate Reality Gaming, Thomson Course Technology PTR, Boston, MA.
Szulborski, D. (2005) This Is Not A Game: A Guide to Alternate Reality Gaming (2nd Digital Edition), Lulu.
Munroe, J. (2005) ‘The Sociable Horde’, The Cultural Gutter, [Online]