As a bonus for everyone who picks up the Halo 5: Guardians Limited Edition, they’ll also be able to claim the Halo: The Fall of Reach Animated Series as well. This animated series, which was animated by The Sequence Group, is based on the novel that tells of the events way prior to anyone even being able to play as Master Chief in Halo.
As the title suggests, this tells the events of the Planet Reach, which many fans of the Halo series will recognize as the located that was a major based of operations for the UNSC, prior to the Covenant glassing the planet.
Halo: The Fall of Reach will only be available in the Halo 5: Guardians Limited Edition and Halo 5: Guardians Limited Collector’s Edition on October 27, 2015. However I imagine that this could and likely will be available later after the release of the game for everyone else.