Seeing as it is set between Oathbringer (#3) and Rhythm of War (#4), ideally you should have read until the third book already to understand what is happening and what it means, otherwise I think you'll be very confused.
Seeing as it is set between Oathbringer (#3) and Rhythm of War (#4), ideally you should have read until the third book already to understand what is happening and what it means, otherwise I think you'll be very confused.