Numerous paperbacks for £1 in M&S!
I just bought '100 years of solitude' by gabriel garcia marquez at M&S in Meadowhall (Sheffield). The book had a sticker on - reduced from £5 to £1. They had various others:
Memoirs of a Geisha
I don't know whether this will work for everyone, but when I got to the till I bought a sandwich, a packet of crisps, and the book. This all came up as "-£0.80". ie, they owed me 80p. The woman said "I'll just charge you 80p for it". I protested; she asked the guy on the next till; he said "Just charge him 80p". So I got the whole lot for 80p.
I think the problem was: They've marked the book down to £1 and also applied a "-£4 saving" discount to it.
Either way, very cheap books - I'm sure they'd go for more than that if you put them straight on ebay!