Wall Street Journal says:

Barnes & Noble Inc. said it exploring a plan to separate its successful but costly Nook electronic-book business as it warned investors that full-year results would show much more red ink than previously forecast.

Shares sank nearly 24% in Thursday morning trading.

"We see substantial value in what we've built with our Nook business in only two years, and we believe it's the right time to investigate our options to unlock that value," Chief Executive William Lynch said.

I guess it makes sense; e-books and book retailing are two completely different businesses, and trying to run them both under a single umbrella must be unwieldy as hell. Still, I think Barnes & Noble is officially in Too-Important-to-Fail territory nowadays—bad news from the only physical book retailer in many American markets is bad news for everyone.