Does Ian Book have a chance at the job?
I think if anything he will continue to prove to be a worthy pick and a player that fits Payton's vision for being drafted.
With that being said I don't believe he starts but will prove capable of starting in the near or distant future dependant on how the top two guys fair once the season starts.
Book could have the same start to his career as previous 3rd-4th round picks at the position in Russell and Prescott. With questions marks at the position why not Ian Book if all else fails and he shows steady improvement.