Thanks to @jane_l on Twitter!
This is puzzling:
Apparently someone did not do careful proofreading of this site. Under Support this is what it says:
Q. What File Formats does nook support?
Nook supports all eBooks, eMagazines and eNewspapers sold at Barnes & Noble.com. You can also load many other files, including MP3s and PDFs, as well as ePub and PDB files.
You can also load images for wallpaper and screensavers using the JPG, GIF, PNG, or BMP formats.
And this must confirm it is using eReader format:
Q. Can I read my nook’s eBooks on other devices like my mobile phone?
Yes, you can read your eBooks across a wide range of devices in addition to your nook. All you need to do is download the free Barnes & Noble eReader app on your iPhone and iPod touch, BlackBerry® smartphone, or Windows® and Mac® laptops and desktop computers. And the eBooks purchased from BN.com will sync between your nook and other reading devices with the Barnes & Noble eReader app, so you always return to the last page you read.
Well, Barnes & Noble does the official unveiling at 4PM EDST today. All of you can go find out more then.