It's a general introduction to things shinki need to know. Things like the relationship with your god, who to go to if your god is malicious, where to learn spells and the fact that pursuing memories of your life turns you into an ayakashi. I'd need to read it myself to know the exact contents.

[He's skimmed over them before, but not enough to actually memorise the information in them. Other than the main important points that he feels are necessary to remember, the rest he feels can be let go.]