Speak with Loremaster Dibbs in Southshore.
[player]. If you don't mind a long journey then I have a task for you, to again help Stormwind fill its library.
The old kingdom of Alterac fell after the great war, and it had a large collection of books. It's a tragedy that the city is ruined, but even more tragic is all of their knowledge lost! We must recover what we can.
Southshore is the closest town to the Ruins of Alterac. Go there and speak with Loremaster Dibbs. He can direct you to the ruins, and to what books may be found there.