I only buy ones that i do not have for my collection. I found a copy of THUD, but as i've already got a copy, it was left for someone else to buy, In fact that reminds me, i have a few books that i've got, that i need to take to the Second Hand shop next time that i'm off
I forgot to say i bought The Science of Discworld, Judgement Day, in Asdas for £9.99p half price on Saturday..