Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of bookseller Barnes & Noble (NYSE: BKS) dropped as much as 10.1% today on moderately heavy trading.

So what: There's nothing new with Barnes & Noble itself, but longtime rival Borders Group is going through a high-profile case of bankruptcy-itis. Borders's announcement of new financing, additional store closings, and a tighter e-book partnership added up to sour grapes for other bookish retailers, including Barnes & Noble

Now what: Barnes & Noble's mid-February rally came to a grinding halt following a terrible financial report and a suspended dividend, and the stock trades some 43% lower nowadays. Fellow Fools have compared Barnes & Noble to the beleaguered heroes of Battlestar Galactica, beset on all sides by and Google, to name just two digital giants that are invading Barnes & Noble's traditional home turf. I see traditional bookstores of all stripes emulating an even more depressing role model.

Interested in more info on Barnes & Noble? Add it to your watchlist.

Fool contributor Anders Bylund owns shares of Google but holds no other position in any of the companies discussed here. Google is a Motley Fool Inside Value recommendation. Google is a Motley Fool Rule Breakers pick. is a Motley Fool Stock Advisor recommendation. The Fool owns shares of Google. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is investors writing for investors.