Ultimate Magic has a section describing several pre-built spellbooks that PCs may use and some of them include preparation rituals. These rituals grant a boon to the caster if a minimum number of spells are prepared from the book. Here (Wiki) are the rules I am referring to.
Are there official Paizo rules for creating and balancing your own boons?
Some useful information I would like included in an answer if possible/applicable:
Are there any rules that outline a PC adding a boon to a spellbook already in his possession? A 3rd party source is acceptable if there is no Paizo ruleset.
Are there 3rd party sources that outline Pathfinder compatible (and preferably well-balanced) boons? This could include 3rd party sources for preconstructed spellbooks. (I would accept this as an answer if there is no official rule-set on the matter. Bonus points if it includes the aforementioned development and PC cost rule-set I'm looking for.)
I've done a Google search on the subject and have mostly come across dead forum posts making the same inquiry. Any sources on the subject would be appreciated.
Note: What I am not looking for are rules outlining custom spell creation and research.