Hooray! Another Moist von Lipwig book! Ah, the perks of suscribing to the Harper Collins newsletter... You find these things out without any undue amounts of searching. Here's the link to the blurb on the Harper Collins website. It's due out in only a few days, too. Amazing how underwraps they seem to have kept it. I remember it being mentioned some time ago - at least, the concept of a book featuring Moist running the mint was mentioned, but this is the first time I've seen an actual confimed release date.
Making Money by Terry Pratchett

Well, we didn't make a secret of it, there's a thread with the identical name just in third place on this page!