Brandor-the-Conqurer
The Bartimus trilogy by Johnathen Stroud.
I love those books. =D So, since you neglected to give a short synopsis, I will provide one for those misfortunates who have not read them:
The Bartimaeus Trilogy chronicles the exciting and amusing adventures of a snarky 5000 (or so)-year-old djinni, who is - to his very great dismay - bound to serve the will of an odious 12-year-old kid called Nathaniel.Voting will take place within this coming week, so hurry up and nominate a few if you have any ideas!