It is a book-cum-work trip of the author and his friends. In short, it is an improvised product, just enjoy it.
"Why do you have a system?"
"Because I haven't seen Lord of the Mysteries."
"... What is this? Is it a benefit to wear books?"
! ! It has little contact with the main plot and has no major changes to the original plot, so proceed with caution.
Concept: What would it be like to work part-time in a mysterious world?