In a filing with the Securities & Exchange Commission, investor Daniel Tisch reported that his stake in Barnes & Noble is now at 8.1%. Separately, B&N announced the introduction of the Nook for Windows 8 app.

In his filing, Tisch reported that, primarily through his TowerView and DT Four Partners firms, he now owns just under 4.9 million shares of B&N.

The release of the new Nook app will allow customers to sign in and shop the Nook store using their Microsoft account. “As part of our strategic partnership with Microsoft, we are thrilled that Nook is the first digital bookstore to support Microsoft account for sign in on Windows 8,” said Jamie Iannone, president of digital products at Nook Media LLC.