Making Money. (Discworld Novel 36), Hardback/Terry Pratchett

'Whoever said you can't fool an honest man wasn't one'The Royal Bank is facing a crisis, and it's time for a change of management. There's something nameless in the cellar (and the cellar itself is pretty nameless), it turns out that the Royal Mint runs at a loss, and people actually want to know where the money's gone.