Enevhar Aldarion
Hero
What level do you need to be to fill up a 100 page book if it is 1 page per spell.
1 page per level of the spell, nor just 1 page per spell, so a level 1 spell uses 1 page and a level 9 spell uses 9 pages. Depending on how quickly a DM allows a PC Mage to acquire new spells, a 20th level mage could have several full spell books, definitely more than one each for just the higher level spells.