"Rimward" fits the entire Eclipse Phase line perfectly, as complement to "Sunward", detailing all factions and places that "Sunward" did not (with one notable exception, the Argonauts). Description of all kinds of autonomists and brinkers is very good, along with articles on Ultimates. There are minor issues that could be addressed better (like better description of economy, maybe along with some solutions in game mechanics), yet the book itself exceeded my expectations, and I consider it necessary for anyone GMing or playing a story in Sol System.