In the descriptions, they each say things like "You can use this book as a spellbook" and "It functions as a spellbook for you", so I expect that spells can be added to them. Am I correct?
[RPG] Can a player add new spells to the spellbooks described in Tasha’s Cauldron of Everything
- [RPG] copy prepared Cleric spells that are also on the Wizard spell list into the spellbook
- [RPG] Can a multiclass Wizard/Fighter (Eldritch Knight) add EK known spells to the wizard spellbook
- [RPG] How does a spellshard spellbook work
- [RPG] Can you use the Telekinetic feat from Tasha’s Cauldron of Everything to break grapples
- [RPG] Can a wizard prepare new spells while blinded
This is correct.
The Wizard’s spellbook feature says:
When the Tasha’s spellbooks say “It functions as a spellbook for you”, they are referring to the Wizard’s spellbook feature quoted above.