Microsoft threatened to sue B&N for patent violations with their Android based tablet. They settled out of court with one of the strangest settlements I've ever heard of. They created a joint company. It was thought the intention was that B&N would agree to make readers for Windows and WP, and Microsoft would get rights to use the B&N eBook division for some planned eReader they were making. None of the above ever became a reality, however, and B&N just paid Microsoft to get out of the deal. That's how patents are involved here, so @fanbaby wasn't wrong there. His trying to slant it as a loss for Microsoft doesn't really add up, but other than that... :)
The bad news from all of this is that it appears Microsoft is going to abandon eBooks entirely. I was looking forward to their eReader software. Now, for Windows 10, we're left with a very horrible Kindle reader, a better Nook reader (that may be abandoned now?) but without the ability to sideload, and very little else. Win8/10 really needs a decent eReader. Preferably one compatible with all 3 of the big DRM schemes (Nook, Kindle and Adobe).