Possible I've just got the syntax wrogn, but for wont of a tutorial showing how to do it correctly, I'mma report it as a bug.

Enchanted books crafted using custom recipes from datapacks behave differently compared to enchanted books obtained through other means.

Firstly, they cannot be used in an anvil as enchanted books to add their enchantments to equipment.

Secondly, they display a cyan name (like other enchanted items) rather than the typical enchanted book yellow.

Please find attached, a screenshot of my mending.json file which I used to create a book, and my attempt to use it in an anvil to add mending to an diamond axe, as well as me hovering over the enchanted book to demonstrate its' atypical name color.