The current political book in the market place is Brown at 10 by Anthony Seldon. Amazon has it at £10.39 [Hardcover] being a 31% discount on the recommended retail price  of £14.99. Surfing around on Amazon will also let you buy it for £7.56. It is 10,644 in Books on Amazon Bestsellers’ Rankings
Similarly Back from the Brink: 1,000 Days at Number 11 by Alistair Darling  is
discounted down from £19.99 (Hardcover) to £10.39 (48%) . Shopping around will
find it for £9.11. However it is 54 in Books on Amazon Bestsellers’ Rankings
Meanwhile Ed: The Milibands and the making of a Labour leader by Mehdi Hasan and James Macintyre  is on the market for £9.97 down from £16.99  (41%). Careful shopping will find it new for £9.46. It is 34,297 in Books  on Amazon Bestsellers’ Rankings.
So what’s the lesson – well markets can go up and they can also go down but these books are heading for Poundland, the local charity shop or else they will be released into the wild (see http://www.bookcrossing.com).