I've yet to try it as I'm already swamped with hundreds of Marvel books when they did the 69p sales, but the text in the email did say: 'Promotion may be used only once per eligible account' Though it doesn't say what makes an account 'eligible'.
Don't think it works for everyone. Itried and I can't pay for the book, just keeps reloading
Hey, thanks. I was sure I selected 'Voucher'. It just didn't click that the page that I was filling in wasn't the Voucher page. (embarrassed)
Thanks @ReviewChimp moved to Vouchers as it's a code (y)