That's really odd.
I bought this book probably back in March or so. I double checked with mine, and I don't have a book cover for this (this is not B&N issue, publisher's issue) as well, but the title is spelled correctly, "The Princess Bride". None of that long extra stuff in the title.
I do find it annoying the Nook ABC's also includes the "The" as alphabetical. Maybe that's why they dropped "The"?
Sorry I'm not much help.
I have sent your findings over to the appropriate team for correction. Once it is updated, you can archive then unarchive to get the correct version showing.
I'm not sure where I would send this request; How about having a link in the eBook section of bn.com that lists any eBooks that have been corrected? I'm not in the habit of archiving my books so it would be nice to be able to check a list to see if I should archive/unarchive to get the newest 'revision' of any of the eBooks I purchased.