It does work offline.
Once you've downloaded the folio to the iPad it stays there and is available without an internet connection.
If it works, works only for Ipad. I'm testing it in a Android device and it works only if you're online, even if the library is already downloaded to the Adobe Viewer.
If you're not online, the Adobe Viewer does not show any library.
It's currently working on our Xoom as it has since May of last year. Sometimes when first opening the viewer app it used to not show the already downloaded folios for a few seconds but I'm pretty sure they resolved that issue months ago.
I continue to have different issues with the Android viewer, but viewing downloaded folios offline is not a problem.
Make sure you're signed in with the same Adobe ID that you used to log-in to the Folio Builder panel in Indesign when you created the folios.
I'm with the same Adobe ID, but if I'm not online, the Adobe Viewer just say to me: "Cannot update your library (something like this)" and I cant do anything inside the app. The Viewer do not show me anything at all. Not even the folios that was downloaded before...
Have you downloaded Bob Bringhurst's free Adobe DPS Tips app? Try downloading his folios and see if they remain on your device.
If you haven't already I would delete and reinstall the app after restarting your device. Sometimes the temp/cache on mobile devices can get cluttered.
Thank you, Andrew. I will try this.