Obtaining this book, and the 4 others, is required for the Master Quest Cape. You must read this book before you will be able to obtain the next one. You do not need to be on Slayer assignment to obtain these journals.
Below is the text you can read from within the book.
This place fascinates me further still. Do the people here even know the genius at work here? The breakthroughs that this place represents?
There are machines here, buried deep within the dungeons underground; machines that can harness and manipulate a person's soul while they yet still live.
Are there others who have studied as I have? Are there others with the vision necessary to push past dogmatic ethical restraints and force this world into a new, brighter future?
But there's more. I have felt it. There resides here a soul of tremendous power, a soul clearly divine in nature, yet it is not whole. It is split across several pieces, many of which have changed to become, of themselves, singular entities.
One soul that has become many.
Imagine! Imagine what we could achieve with such a thing. A single person could become an army, or a kingdom. They could create multiple versions of themselves with which to seek out more experiences, and in so doing grow ever more powerful. One could take these parts and combine them again, to become something greater than the sum of those parts. A god! One born not of dalliances with ancient artefacts, but one that truly deserves the moniker.
A god who has earned their place among the stars.
This I must investigate further!