I made my first sovereign and gave him 3 schools of magic, only after looking at the premade ones did I notice they all had all the spell books available.  So to stay competitive I remade my sovereign with all the spell books.  I know other people had mentioned other ways of limiting the amount of spell books available to everyone.  I think its something that at some point needs to be addressed however not necessarily an immediate concern except maybe on multiplayer.  I was curious on hearing more ideas people had on it.  I'm sure there are those who are fine having access to all the books from the get go and I would enjoy hearing their reasoning as well.  Mixing one or two things I've heard others say I think either increasing the amount of points each successive book on a custom sovereign costs to get goes up far more, or limiting it to say 2 schools from the get go with needing quests or researching other schools of magic as the game progresses.  I thought I had also heard that originally you needed the appropriate shards to use that school of magic.  I don't know if that was true or i mixed things up a bit.  This also sounds like a good idea, except for the fact that you would need to give the sovereign some magic to begin with.  So maybe he can choose 1 or 2 schools to already be able to use.