Well, if you believe the license that you "agree" to when you buy an ebook, you can not sell an ebook. So--on that basis--you should not be able to sell an ereader and have the sellers purchased ebooks survive the switch to your account.
That said, I'm in the US where the law is that for physical books, the publisher (or any seller) can not prohibit further sales. So I see the ebook "license" as an end-run around the Supreme Court case holding that on-sales can not be barred.
