u/Fleecejakke

I found the legendary magic item "Tome of the Stilled Tongue" from the 5e DMG, it states that "While holding the tome, you can use a bonus action to cast a spell you have written in this tome, without expending a spell slot or using any verbal or somatic components." once per day. Can a spell be cast in this manner even though a 1st level or higher spell has already been cast? Similarly with some sorcerer abilities to cast spells using sorcery points instead of spell slots to cast, like from the Abberant mind Sorcerer.

Thanks in advance.