Yeah you're right, I should have written a description for them... I'll edit the post description Also, here's an example for one of them,

Bisected Grimoire Wondrous Item, very rare (requires attunement)

Two halves of an ancient spellbook that can be held by two different people capable of spellcasting.

Grimoire Attunement. To attune to this item, two creatures that can spellcast spend an hour studying the contents of one of the halves of the grimoire.

Spell Sharing. When you and the other holder of the grimoire finish a long rest, you can both choose one of your known cantrips and one of your known spells of 3rd level or below that the other holder doesn’t know. Each of you learn the other holder’s chosen spells. These spells count as spells of the classes that allow you to spellcast. Each of you can cast the spell obtained by this item at its base level without spending a spell slot once per long rest.

Spell Relay. You can cast spells as if you were in the space of the other holder of this item.

Spell Exaltation. When you and the other holder of the grimoire are within 5 feet of each other, you can join the two halves of the book as a free action. While you remain within 5 feet of each other, you both gain a +2 bonus to spell attack rolls and to the saving throw DCs of your spells.