What's perhaps most interesting about Fire and Blood is that this isn't a novel (or part of a series of novels), like Martin's A Song of Ice and Fire. Rather, it is a fictional history of a fictional world. Moreover, consider that it is presented not as Martin's own world, but as a transcription of a history from within Westeros itself. In essence, this is both a history of Westeros as well as an artifact of Westeros, which creates interesting conundrums as to its historical accuracy (and a very interesting variation on the idea of unreliable narration).
The overall sequence of events can probably be trusted as an accurate account of Westeros's history. For example, the various Kings have ample evidence of their rule, as lines of succession and genealogies would all have been established knowledge within Westeros itself, as would the events within each rule (wars, marriages, etc). However, it is worth recognizing that, within the context of Westeros itself, Gyldayn (the fictional author of the historical text) would have been far removed from the events and personalities he is writing about. There are therefore doubts that arise in relation to his account of their personalities and the various personal stories he recounts (in particular his own suppositions about those various stories).
One notable example can be seen early in the book in his treatment of Aegon I's sister-wife (term for a woman who is both a sister and a wife to her husband) Visenya, one of the quasi-legendary figures in Westeros. The basic history is well established—about the conquest and establishment of Targaryen rule and Visenya's own role in this—but then Gyldayn starts writing about rumors concerning her turn towards sorcery and even notes that some believe she was a kingslayer. Additionally, it is worth wondering the degree to which the reputations that various rulers have since acquired might have influenced Gyldayn's own reading and perspective concerning them. This is a work where myth and history are so deeply interwoven that it becomes difficult to separate where one ends and the other begins.
Finally, one of the most fascinating aspects of Martin's work arises in how he interweaves smaller stories within this larger historical narrative and the degree to which those smaller stories are often treated in an open-ended fashion...
(The entire section is 581 words.)