Game of Thrones : les origines

The book feels like a treasure trove of lore, but I wonder how he chose which stories to tell and what to leave out. Did any details surprise him as he wrote?

The world-building is incredible, but I found myself getting lost in all the names and histories. Was this intentional to convey the depth of Westeros, or could it have been more streamlined?

This book adds so much context to the stories, but I’m curious why it was structured as an extension rather than a separate universe. How does that affect the storytelling?