This is a great supplement for both players and GMs. It is primarily for players, with lots of options for character creation, advancement, and ideas during play. However, the background on the world and rich thematic substance of the book makes it fertile soil for adventure ideas and other GMing tools. I am currently both GMing and playing Soulbound between two different groups, and am extremely excited about this book from both perspectives. The rest of the group has been extremely hyped by the release as well.
Overall, I would consider this part of my gold standard in player supplements, and eagerly await the rest of the line with this as an entry.