Affinity Tomes
"Affinity tomes contain detailed reports and information gathered by magi over the years pertaining to a specific affinity.With the exception of the General Affinity tome,they will,when read,give a 10% boost to that specific affinity,while simultaneously reducing your progress in all other affinities by 10%" -Arcane Compedium's Description with some minor vocab/grammar changes.
More about Affinity Tomes
The only affinity tome you can get is Affinity Tome : None which can sometimes be gotten from Dark Mages.The other tomes are currently not able to be obtained without cheats or mods ( making custom recipes using Minetweaker,etc.).