[Madam Broshkina]

I believe if he registers the reader to his own account the books that you bought will not work on his reader. You could I suppose let him register the account in your name because you can authorize up to six readers/computers per account. That might be a good option if you both like the same kind of books (in which you can split the costs) or can trust him not to go crazy buying books unless he will reimburse you.