This is a common problem users are getting for different things like books and apps for last few days.
Perhaps the CS rep doesn't know what he/she is talking about.
What happens if you try again.
I got this in one app on all 4 Nooks and on retrying it worked for all 4 Nooks.
Other users got this with books.
Did you get your book to download to your Nook? I was able to download a free sample of their most recent book today to an NT (and the free sample option wasn't even showing up the other day for almost all the November releases.) It opens fine and .....it looks like will need to delete this asap before my mother sees it (some things you never outgrow!)
It almost looks like you picked a book to purchase while B&N was in the middle up updating their nookbook data base (however it is that they upload them.) Having said that, currently a search of "sirenbookstrand" from the B&N website will result in 2376 books. A search on the NT will give you the same quantity. But if you search from the HD+, you get a total of 4 older books (from 2009 and 2010.) Right now it looks like this publishers books aren't compatible with the HD+ which really makes no sense. You're right, they're just epubs.