Q is the narrator, the point of view, in these books, though there is a couple of chapters from other characters perspectives. He would also be considered the male protagonist of the series.
Q is a 13 year old boy, biologically the son of Blaze Munoz (Singer) and Peter Paulson/Speed (Guitarist). He wants to be a magician (though people think he means musician) and his idol is Houdini.
Since he wants to be a magician, he always wears clothes with a lot of pockets, typically cargo pants. They are typically filled with multiple decks of card, scarves, fake coins, and plenty of other odds and ends. This sometimes comes in handy during the course of the story.
Q is one of the only people that know about the Ghost Cell that is not politically important, part of the family of the formerly mentioned group, part of the Ghost Cell, part of or formerly part of an intelligency agency, or wants to be part of an intelligence agency. He is sort of how one of us would feel if we got stuck in the middle of this situation. That makes him relatable, a very good choice for a narrator.
Q makes for a great addition to these books,and they wouldn't be the same told from anyone elses perspective.