Confirmed
The tower lists ten grimoires with Epic 50, Legendary 100, and Mythic 250 pity counters linked to Mana Crystal. It says some subscriptions reduce pity by 30%. This is not a complete description of the roll UI or replacement rules.
Race, social class, and trait cards separately publish normal/special rates. Their text does not establish the current menu path. A character spin result is not evidence of a book-change procedure.
Not confirmed
Whether a roll overwrites a book, requires dropping one, or stores another copy is unverified. The bag permits up to 2 copies of each grimoire, but gives no active-book controls. Finral lists the tower for previously visited destinations; it does not establish a first-visit shortcut.