Hello there,
I was looking at something similar, custom spellbooks. Probably you can tell me whether and I hope how my project is feasible.
I understand that there are several spellcasters: paladin, mage, necromancer, ninja, spellweaver, gargoyle, each with a specific skill and a different set of spells. Did I forget any?
I am a fan of character class systems, but I have always found some spellcaster classes to be unbalanced. I would like to define my own classes and re-dispatch the spells according to what I believe is more coherent + I would like to promote teamplay and interaction with characters that must complement each other.
For example, I would first like to make a difference between profane and divine magery. Divine magery would be used by a priest and would include paladin + the healing, curing and blessing spells from the mage that would be removed from the mage's spells.
With the profane spells, I would create a system using specialization schools similar to the system in Baldur's Gate, i.e. a specialist can use spells from all the schools except the school opposite its specialization.
http://baldursgate.wikia.com/wiki/Specialist_Mage
Including the bushido book, I count 6 books available (bushido, ninjistu, chivalry, magery, necromancy, spellweaving), thus 6 possible specialization schools.
And as the result of the solely exclusion of the opposite school, each profane spell would be used by the 5 remaining schools.
There is still the case of the bard. I have not decided yet what to do with this one.