Here’s the B&N eReader app for Windows Mobile from the HD2 NRG ROM, now it’s .cab ready.
Tapping on the ebook from the homescreen gives you an overview of the book and even more detail if tapped again (pics below). You can also shop for more ebooks. You are actually again brought to your browser to shop and if you pick a book when you go back to the app you push ‘sync’ and then it appears in your list to download. When you start the app it also auto-syncs.