The Book (Perjour) appears in the Lores and Histories story Twice Burnt, which is supposedly an extract from Perjour's book. It was found in the TzHaar City library, possibly left there before Perjour went to try and find the Elder Kiln.
Perjour was a chronicler for Zaros, bound to his book with magic that made everything he thought and experienced appear on the pages of the book for Zaros to read later. This was so Zaros could know exactly what happened on missions and campaigns that he was not personally present for.
At some point the book's magic was influenced by Zamorak, who created a duplicate of the book that would show what Zaros would want to hear, as dictated by Perjour's fears of displeasing Zaros. The original book still told the truth, but Zaros would only see the false version. Zamorak created this false copy to hide his impending betrayal from Zaros, who often sent Perjour to chronicle his missions.
The book's author could also be changed to others, as demonstrated by Zamorak after the dancer Char was captured by Fremennik. It is unknown if this is an original feature of the book or if it was something only Zamorak could do.
The book has black writing when Perjour is the author, and gold writing when Char is the author.
- Perjour is French for 'per day', as jour means day.