Currently, I'm reading Dumas' Musketeer Romances* on my Nook.
There are a lot of great books out there in the public domain, and available in electronic form on the Net. Reading them on a desktop or laptop computer is a chore, but these little Ereaders are great for them. Classics of literature, classics that aren't really literature (There are something like 30 of Percy Keese Fitzhugh's Boy Scout novels - Tom Slade, Pee Wee Harris, Roy Blakely - in the public domain and available online.)
I've had mine for nearly a year, and I don't think I've bought more than a handful of books. And most of them from Baen's web subscriptions, rather than from B&N.
*"The Three Musketeers", "Twenty Years After", "The Vicomte de Bragellone", "Ten Years Later", "Louise de la Valliere", and "The Man in the Iron Mask" - as epubs from Project Gutenberg.