I just came across a trade in offer from Sony. The Gadget Show is reporting that if you bring a paper book (any book) in to a participating store you will get £20 off the price of a Sony Pocket Edition.
This deal is a tie in with World Cup, and from what I can tell it's only good for the UK. I've confirmed that the trade in offer does exist but I'm not entirely sure that it applies to paper books. Buyer beware. BTW, here is a PDF with all the Sony products covered by the offer.
The Gadget Show is also reporting that if you register your Sony Reader before 11 July, you'll get special “Love soccer” or “Hate soccer” ebook package with 5 titles.