Kyle is as famous as he is due to the Game he starred in, "Dark Forces" or something like that.
He isn't a main character in NJO but he is frequently involved in the events. And in the NJO Series he becomes Battlemaster.
He hasn't really been in anything where he is a main character. But he is in allot of books that The NJO is greatly involved in, like Swamp War and Dark Nest..
I have the Dark Nest trilogy and Kyle didn't do a whole lot. It's a shame there isn't a book where he is the main character. He is a great character and I feel a book about him would be really good, of course the author has to write him good too. I'll have to check out Swamp War then.