Snyder told the site he has spoken with the graphic novel’s creator, Frank Miller, who will be writing and drawing the graphic novel that the second film will be based on. Work on the script for the movie won’t start until after completion of the book, as Snyder doesn’t want to have any input into the novel and wants it to be Miller’s creation.
The director added that it will take place between the Battle of Thermopylae and the Battle of Plataea, the battle that narrator Dilios (David Wenham) is at the end of 300. There’s a whole year between the two battles and plenty of room for more story.
Snyder said he would definitely direct the follow-up.