This book details suggestions for persuading and inspiring others, but entwined with the words is a powerful magical effect that permanently increases a +2 inherent bonus to Charisma to a +3 inherent bonus to Charisma.

You must have a +2 inherent bonus to Charisma from using a tome or upgrade tome in order to use this item.

The maximum applied bonus to an ability score from Inherent bonuses is capped by character level, but you can have potential bonuses higher than that. At level one and two, you cannot benefit from any Inherent ability score bonuses. Applied bonuses to your character are unlocked with higher character levels:

Level 1: +2
Level 3: +3
Level 7: +4
Level 11: +5
Level 15: +6
Level 19: +7
Level 22: +8 and higher