This question strikes me as odd for two reasons - firstly, because it's difficult to believe that an educator would confiscate a book, and secondly, because for some bizarre and inexplicable reason, you were compelled to ask this anonymously.
Few educators would be of the opinion that it's a good idea to confiscate something like a book - especially when it's a book that the student is reading for pleasure. Of course, if you were sitting in math class and decided to lose yourself in a novel, it would be pretty understandable if your teacher decided not to stand for that, and in all fairness that person would be well within his or her rights to take it away.
One day, it can only be presumed that you will finish school, and the time will come for you to go out and get a job. If I were your boss and I were paying you to complete tasks, I'd expect that in exchange for your salary, you'd be focused on the job and not on something else. And I think that if I were to discover that you felt you had other things to do than to attend to the tasks I assigned you that I would't have any issue making my displeasure known to you in whichever manner I happened to see fit.
Your job is to study. You can read at home. That's where distractions belong. Just because you happened to be reading instead of texting or watching a video or playing a game, that doesn't mean that you didn't break the rules.
Tell your teacher that you realise that it wasn't the time or place to be engaged in a book and that you've learnt our lesson. My guess is that ought to be sufficient to convince the person to release your book. If it isn't, then you can mention that you've already apologised numerous times and that whether or not it's classroom policy to confiscate the item in such circumstances, the fact of the matter is that as a minor, each and every thing you own really belongs to your parents, and if the book isn't returned you'll have no other option but to involve them which would likely lead to a conversation with the principal or headmaster/headmistress.
It's doubtful that anybody wants it to go that far, so the real question is: "Are you telling the truth and the whole truth or not?" Because if it really is a book that's been confiscated, I can't see why you haven't done this already. It makes me think that you're avoiding escalating the matter for some reason, and the only logical one is that you don't want your parents to know this happened in the first place.