Hmmm...
Wow. Having read this and other threads about graphic novels and illustrated Eric etc, I'm starting to think I'm sat on a bit of a goldmine.
My Pratchett collection - including aforementioned graphic novels/illustrated Eric etc - are all first edition prints with the exception of TCOM, LF, ER M and S.
I have the hardback and paperback editions of all UK Pratchett novels since (as purchased on UK release date).
That's what happens when you work in the city centre - I used to visit Waterstones, Dillons and HMV every single lunch hour and whenever anything Discwolrd was released, I just bought it on the day!
Will never sell personally of course, but handy to know there maybe a small nest egg in them for my kids (unless I can convince the little buggers to actually READ them first . . . . . ).