Their search results are messed up and vary based on whether you are signed in, so I do know it is account based, but they do exist on the US store with US dollar amounts attached to their price, they just don't show up if you sign in. If anyone else is as disappointed as I am about this, it probably wouldn't hurt to let the publisher know how you feel. The best advice I can give you is to periodically check our website for updates. Unfortunately, we have not heard any information about further publications but please keep in mind that we do not generally know about publications much longer before the public is made aware. When I contacted the publisher, this was their response: Here's a list of all the books that Penguin Audio currently has no plans to make available:

TL:DR Only three Watch books will be available, and zero of the the Moist Von Lipwig or Tiffany Aching books!

After doing a little digging, I discovered that none of the books following Hogfather have US release dates.

As has already been discussed in a couple previous threads, Carpe Jugulum is not available for purchase in the US due to a distribution rights issue.

Download tiffany aching