It is rare that going into a bookshop saddens me, but it did so last week. Going into any half decent bookshop in December any time in the last 20 years or more inevitably meant encountering a large pile of the latest hardback DiscWorld novel – the easiest item on my Christmas list. But this year it was missing, a big gap – no more Librarian, no more Sam Vimes, the world’s best policeman (someone should do a spin-off series featuring Sam, solving crime in Ank-Morpork, with the aid of his raggle taggle army of recruits), no more Veterinari, no more Granny Weatherwax or Ogg. Really sad.