Forbidden Tome

(Requires attunement)
If attuned, you can use it as a spellbook and an arcane focus.
While holding the tome, you can use an action to cast a spell of 3rd level or lower you know, without expending a spell slot or using any verbal or somatic components. Once used, this property of the tome can't be used again for a month and a day.
Cryptic messages appear in the book. These messages appear at midnight and fade away after they are read.