I'm reading a MOBI edition using the Kindle for Android app on my Nexus 7 tablet (which just got updated to Android Marshmallow 6.0, for those who care). The author sent me the manuscript as a DOCX file, I then saved it as an RTF file; using Calibre Ebook Management software, I then converted the RTF file to a MOBI file -- and then saved the file in the Kindle folder on my tablet. Works for me!
You can read about my work on the previous Laundry Files novel, The Annihilation Score, in my March 26, 2015, blog post. But as to The Nightmare Stacks, you'll probably have to wait until after the New Year, as the project is due back to Ace Books the beginning of January. (Yes, another set of holidays I must work through, sigh....)
The Nightmare Stacks is due to be published by Ace Books, and Orbit Books in the U.K., in early summer, 2016.
But, ahem, I get to read the novel now.