Book content is still being ported, stay tuned!
Gregoran's story plays in a universe in which GMs may never start a campaign, nor allow travel to. It is following the life of Gregoran, who was the very first NPC (!) of this game to finish his life cycle, and to give players a taste as to what to expect in the game as much as giving readers an idea regarding how the Tome of Records will be kept.
Said story is commonly told and spoken about in various locations and in various universes, due to the impact Gregoran had on the world in the course of his life as well as the role he would finally play in the greater scheme of things. As everything else that can be found about the RPG, this story is uncovered during gameplay (as it also contains more than just a few more-or-less hidden facts and schemes of this world) and will be expanded accordingly. This may also result in different parts of the story being uncovered - and end up in a state of chronological chaos at any given point in time. That said, any uncovered parts will still be easily identifiable in their relative order to things - they retain any chapter numbers etc.
In other words: Don't be surprised if chapter 17 follows after chapter 8 - this merely means that chapters 9-16 haven't been uncovered in gameplay sessions yet.