The Schools of Arcane Magic - Mastery is awarded from completing the Higher Learning achievement in Dalaran.
Patches and hotfixes
/ Patch 3.0.2 (14-Oct-2008): Added
Using this book allows you to teleport to a spire atop the Violet Citadel. You may then receive a [Kirin Tor Familiar] non-combat pet after speaking with Archmage Vargoth.