Starting setup:
3x Life
3x Chaos
3x Nature
1x Sorcery
Node Mastery
I played the game to see how many spells I could get (3 books in a magic colour allows you to trade for very rare spells and get very rare spells from lairs, nodes, etc.). I found the 2 extra sorcery books I was hoping dearly for :)
I ended up with so many spells that, where the research cost of the Spell of Mastery is reduced by 50% of the research cost of all the other spells that you know, by the time I researched the Spell of Mastery, it cost me zero to research

Most of the reason I got a big score was that I would only ever attack the AI wizard's fortresses, never any of their other cities. Every time you take their fortress, you can get a couple of their spells, so I was trying to continually banish them, let them cast the Spell of Return, then re-banish them to try to get more and more spells. By the end of the game, doing this had given me 461 fame which accounted for a big portion of my score.
Implode.