If "Book of Moon" is used on an attacking monster, then that monster is no longer considered to be an attacking monster. Thus, if "Book of Moon" is Chained to an effect like "Dimensional Prison" or "Sakuretsu Armor" and changes the monster to face-down Defense Position, then the effect of "Sakuretsu Armor" does not resolves, so the attacking monster is not destroyed (or removed from play, and so on).
These TCG rulings were issued by Upper Deck Entertainment and have since been deemed unofficial by Konami. They were previously considered official and can still be correct, as long as they follow the official gameplay rules, or unless Konami has issued a ruling that says otherwise. References: 
↑Konami Judge Program Rulings are considered unverified, as their source(s) are not publicly viewable. They are not confirmed as applicable to the TCG until they have been officially published by Konami.