The Authors Note at the front of Her Majesty the King says that most of the characters are real. How can you know what people who lived so long ago were like?
For some characters, like Hatshepsut and Senenmut, numerous statues and inscriptions have survived that can give us some idea of what they looked like, what they cared about and what sort of public persona they presented. But for most of the characters, very little hard information is available apart from their names and their highest-ranking titles. Often, we dont know all the offices these people held on their way up the career ladder, so in the period of time covered by Her Majesty the King, if characters havent yet achieved their ultimate rank, they were placed in positions typical for officials advancing to those ranks.