Soul journey is a book written by Aretha found in the Arceuus House Library in Great Kourend. Customers in the library may ask the player to provide the book for them, after which the player is rewarded with Arceuus House Favour. The book is required to begin the Bare Your Soul miniquest.
After reading the book for the first time, the chatbox will state The book referred to an artefact being buried in Kourend, but the author did not specify where it was buried. Maybe you could persuade her to change her mind.