SDN calculations are 120 questions that all you need to pass naplex calculations. Its is not a book, it is just a soft copy of about 24 pages(not sure) floating arround. They are free to get if you have a friend that has it.
About the quiz bank, I think there is legal consequences if somebody share the password. That what the people who made the quiz bank said on their website, so it is up to you. You can also buy a one month access it is cheaper .