Microsoft has a record of buying up successful (and not so successful) businesses and folding them into its core operations. It's not a great record mind you, but its the way Microsoft have done business for more than two decades.
Latest candidate for the Microsoft dollar is Barnes and Noble and its Nook eReader. Why Microsoft should see value in the purchase remains a mystery to me. Things are bad in some if its core businesses, but is it seriously hoping to compete with Amazon in this space. Even Apple, which has a following much more likely to spend on content and a walled garden ecosystem which actually makes it more difficult to purchase from Amazon, isn't seeing great success on this market.
And that's ignoring the fact that Microsoft had a (relatively) successful eReader platform long before any of the current players in the market.
That Microsoft abandoned its Reader product and store in the past, plus its past history with Plays For Sure media DRM - whose customers were also thrown to the sharks - isn't really going to inspire a great deal of confidence in whatever it is Microsoft has planned for Nook.
All things considered, Microsoft have got bigger problems to focus on. And it's doing that badly enough without adding in any more distractions.