B.
I would not buy one for a 10 yr old. they are really expensive. just by him some real books.
you will spend about the same for the book in ebook format as you will in paper format. But he can't trade them with his friends or take them to a used bookstore and sell them back. you can trade between nook readers but the other person would have to have a nook as well.
Also he wouldn't be able to take it to school with him and read his books at school , it would likely be labeled an electronic toy .