Cheapest I've seen this recent and superb Batman graphic novel by the genious that is Neil Gaiman and beautifully drawn by Andy Kubert. Amazon (gawd bless 'em) have pricematched - so I've put Amazon link in post below - but no Quidco there.
New York Times" Number 1 best-selling author Neil Gaiman takes on The Dark Knight! Neil Gaiman, co-creator of "The Sandman" and writer of "The Graveyard Book", re-teams with his collaborator on Marvel's 1602, superstar artist Andy Kubert, to tell the story that delves into life, death and the afterlife, leaving no stone unturned and exploring every aspect of The Dark Knight's life and crime-fighting career. This tale parallels the classic "Superman: Whatever Happened to the Man of Tomorrow?" epic, written by Alan Moore.