Microsoft is offering to pay $1 billion to buy the digital assets of Nook Media LLC, the digital book and college book joint venture with Barnes & Noble and other investors, according to internal documents. In this plan, Microsoft would redeem preferred units in Nook Media, which also includes a college textbook division, leaving it with the digital operation — e-books, as well as Nook e-readers and tablets. The documents also reveal that Nook Media plans to discontinue its Android-based tablet business by the end of its 2014 fiscal year as it transitions to a model where Nook content is distributed through apps on “third-party partner” devices. Speculation about the plan to discontinue the Nook surfaced in February. The documents we have are not clear on whether the third-party tablets would be Microsoft’s own Windows 8 devices, tablets made by others (including competing platforms) or both. Third-party tablets, according to the document, are due to get introduced in 2014. Nook e-readers, meanwhile, do not appear to fall into the discontinuation pile immediately. Rather, they’re projected to have their own gradual, natural decline — following the general trend of consumers moving to tablets as all-purpose devices.