Bio-Infusion (Spellbook)

A Bio-Infusion is a magic item that attaches to your arm, becoming inseparable from you as long as you're bound to it. To bound to this item, you must hold it against your forearm for the entire 1 hour ritual.

As a bonus action, you can retract the Bio-Infusion into your forearm or extend it from there. While it is extended, you can use the item as if you were holding it, and you can't use that hand for other purposes.

Given this is for a spellbook it's magic is stored inside and can be used only while it is out. And it repaired as it is inside one's arm, also you can use this item to turn into a spellbook as if by polymorph rules.

This spellbook, along with anything written on its pages, can’t be damaged by fire or immersion in water. In addition, the spellbook doesn’t deteriorate with age.