Although James S.A. Corey / Daniel Abraham tweeted a link to hachette group books' website to announce the release of a couple of chapters, it is the overdrive site that offers us more!!
Four and a half chapters as well as the Prologue and the Table of Contents.
From this we learn the viewpoint characters but more surprisingly, we discover the over 30 year time leap!
Sample Chapters on Overdrive
https://www.overdrive.com/media/3198887/persepolis-rising