Ubisoft and New Regency have hired Michael Lesslie to write the script for their big screen adaptation of Assassins Creed. X-Men: First Class star Michael Fassbender is already to set to star in the film, but it has yet to get a director.
I don't know much about the screenwriter, but according to THR he's an acclaimed English playwright, who wrote Prince of Denmark, "which was performed at the National Theatre in 2012. He also has penned a number of short films including last year's Skirt"
Ubisoft will maintain control of key elements of the movie's creative direction, so they will be guiding the writing in the direction they want the story to go. I imagine it will stay close to the story of the video game, which centers on a bartender who is captured by a secret corporation with ties to the Knights Templar, and learns his ancestors were trained assassins. He's sent back in time to retrieve historical artifacts.
If you've played the game, then you know the awesome potential that the film franchise has. It could be such a badass movie, hopefully they don't hire Paul W.S. Anderson to direct it.