Both the full refund (for gems) and partial refund are really expensive if you only want to make adjustments to a single skill. Maybe there should be 2 additional options along the lines of:
1) Destroy a single book assigned to a skill.
2) Refund a single book at ~60 gems per book.
Currently it costs 50 gems per book to refund everything, so it would still be cheaper to do that if you wanted to make a lot of changes.
Obviously the remaining skills would need to follow the skill tree rules, so if you decide to remove some skills from the middle of the skill tree then it would disable any skills higher up the tree until enough books have been re-invested.
Merged