As near as I can tell, there's no rule that requires any kind of personalization of the ritual book -- assuming each PC ritual caster spends 8 hours on it, can they master rituals out of each others' books? And can they all share books that they find as treasure?
Other than the importance of backups, is there really any good reason to have more than one ritual caster in the party?
On a related note, the economics of the market price of rituals doesn't make much sense to me; anyone can copy from an existing book, so why are the market prices so high?
Other than the importance of backups, is there really any good reason to have more than one ritual caster in the party?
On a related note, the economics of the market price of rituals doesn't make much sense to me; anyone can copy from an existing book, so why are the market prices so high?