User blog comment:Menara/The Son of Sobek: The official PJ and Kane Chronicles Crossover/@comment-117.195.154.59-20130508105015/@comment-3146930-20130508211257

It isn't wrong. The Son of Sobek was released as a bonus with The Serpent's Shadow. The information above doesn't state that it will only be limited to paperback books. However, The Son of Sobek will be released by itself with the HoH chapter exclusively in e-book format with Rick Riordan reading it.