The opening story combines the intense political manoeuvering of the Silver Ladder with action, negotiation, power plays and high drama, a riveting read in its own right. The Introduction then draws out the main theme that concerns this book: scanctums. Even Sleepers have homes, places in which they feel safe. A mage's sanctum in so much more, a place to study as well as somewhere to rest, recharge his energies and far more. But in such places you find the bedrock of mage society, individuals and cabals. From there the greater assemblies arise, but the cabal is the core bastion against the Abyss and other threats, and the central point around which Awakened politics revolve. Assembkies and other groupings are made up of cabals, not divided into them. The cabal and the scanctum it uses is the mage's refuge, shelter, the place to return to when the work is done... or when something nasty is chasing you. Sanctum and Sigil, then, starts with the permutations of Awakened politics, from the inception of a cabal and the inter-cabal politics of a Consilium right to the mage's home - the sanctum. It provides details on the inimical opponents that move to hinder such institutions and the magical resources that are used to protect a sanctum.
First up, Chapter 1: The Polity explores core concepts about how a cabal is set up - will it consist of mages from but one order or the more modern pattern where individuals of several traditions join together. It looks at a cabal's protocols, the rules that govern members and the oaths that bind them and the sigil that is their symbol. Then it moves on to the Consilium, the forum where inter-cabal politics play out, and also the 'Lex Magica', the laws that govern mages and their use of magic.
Then, Chapter 2: Pride of Place looks in detail at the physical - and magical - construction of a sanctum. Essential reading when your cabal comes to set down roots. There's also plenty of information about Hallows, ley lines and Demesnes too.
Next, Chapter 3: Pylons and Cults examines how the opposition organises itself. Banishers of course, but also Seers, those lost souls that seek far past Watchtowers into the far depths of mystery - but what do they do and why are they a threat?
Finally Chapter 4: Storytelling explores how to actually run all those political machinations and make them really come to life for your players, get them to care about the outcome. There are also ways to get your cabal into trouble (if they don't manage to find it for themselves) and three sample cabals you can drop into your own chronicles: a Pentacle cabal, a Seer pylon and a Banisher cult. Ready-made rivals, opposition, threats...
This book makes for a fascinating read, but you do need to be well-embedded into Magic: The Awakening traditions and terminology to make the most of it. The material herein will aid you in building a deep, rich, vibrant world for your mages, one in which there is plenty going on and with opportunities for them to get involved (whether they like it or not) at every turn. Drag the more bookish mages out of their studies, make the muscular ones stop and think about the consequences of their actions, devise and run the local power structures of mage society with a sure hand... well worth reading if you want to scale the heights (and plumb the depths) of a living world and make your mages far more that mere spellchuckers but part of a real community that exists just out of reach of everyday Sleeper life.