Finding this text is a requirement for the Master quest cape. See Tips and Tricks to obtaining the Master Quest Cape for assistance obtaining the Master quest cape.
If lost or destroyed, a new copy can be obtained from the bookcase in your Player-Owned House made through Construction.
Below is the text you can read from within the book.
My newfound control over my mind is a revelation almost as great as that which allowed me to discern the Link. With the deaths of more of the False Users, the curse has diminished to such a degree as I can resume my journals. The fact that the previous volumes have become as dust in the meantime shows how long I have been beset by agony.
Even as my control over myself grows, the foolish Dactyl subject tries to exert control over our group. What nonsense! I have slain the most False Users here. I should be in command. Even Strisath's compliance with my commands shows this. A confrontation is brewing.
Kalibath is the unknown quality to me; I have seen him only once before and that was centuries ago. Can I trust him to back me when the time comes? I am unsure. I have seen him sneaking around this hovel. I know he has captured one of the humans for some reason. Amusement? Food? I know not. He also seems fixated on the idea of attacking Saradomin next, which seems like folly to me. That False User is powerful, and we will need more items from the Vault to drain one such as he. On the positive side, having seen how the Dactyl has swollen with power excites me greatly. To imagine myself bursting with such energy makes me salivate at the possibilities. The people of this and the other worlds would be nothing before us, and the False Users less than chaff in the wind.