Microsoft is officially closing the chapter on their LIT format for reading books via the MS Reader Application by August 30, 2012. You will still be able to download the reading app until then and buy books.
The MS Reader application was one of my personal favorites and it worked really well on Windows based tablet computers. This was a solid program to read books that you downloaded from the internet or converted to LIT format. It was an easy to manage program and had a good interface.
MS has not commented on what the future holds for their e-reading application.