They've knocked £10 off the price of the Kindle, bringing it to an appealing £59. This is the basic model Kindle, which means it lacks the touchscreen, frontlight, fast CPU, or other frills found on the more expensive models. On the other hand it also has an ever falling price, which is itself appealing.
The retail giant faces perennial pressure in the UK from any number of competitors. Today it might be Sainsbury's, but tomorrow it could be Sony, and then Nook, Kobo, or even Tesco (at some unknown future date), each of which might throw a sale in order to attract customers.