Kill Jarko (yourself) (beware he is strong), and take his Book of Spells.

Bad Alignment Option (Ogrimar):

Take the book to Araknor, northwest of the temple of Lighthaven, saying the word grimoire.

You can complete this quest at will.

Gain:

• 300 gold coins
• Ring of Darkness or Ring of Confidence
• You become the apprentice of Araknor the Necromancer (unlocks The Blind's spells on Raven's Dust)

Good Alignment Option (Artherk):

Take the book to Lord Sunrock, the WindHowl Mayor, saying the word grimoire.

You can complete this quest at will.

Gain:

• 300 gold coins
• Gold ring