An essential addition to the core M20 rules -- if you want paradigm, reality zones, and the battle between different visions of what the world means and how magic works in it, this is a supplement will make your game sing. The writing is clear and direct, the rules well-thought out and balanced, and best of all there are slews and slews of colorful and detailed examples to really breathe life into what characters and factions believe and how those beliefs interact with Sphere magic. This should have been part of the core book.