Describing itself as a book about power, it is really a book about ambition - and how to empower your characters to reach even more dizzying heights than even they might have dreamed about. For this book contains the tools you need to play full Inquisitors and sets the scene in which they operate: unbridled power and freedom to act, full of politics and intrigue... and the consequences that such responsibility brings. It's a mix of solid game mechanics and insights into how to play (and game master) characters at such exalted levels.
It starts off by presenting the necessary mechanics to take characters beyond the eighth rank in their chosen career and introduces a new system of Influence to model how characters at this level wield their authority. From here it moves through various other aspects covering the transition from Acolyte to Throne Agent and beyond - skills, new career paths, psychic powers and even a visit to the armoury. These chapters give you all the information you need to make this transition happen.
The second part of the book looks more at the 'what' of the transition to power, this ascension, than the 'why' that has already been covered. Key here is a chapter on 'Serving the Inquisition' that explores the very nature of the body in which characters are aspiring to take a leading role, and the ways in which such senior individuals can exert an influence.
As Acolytes, characters serve best by following orders (however much latitude they may have in interpreting those orders and figuring out just how to accomplish the tasks they've been given). As Throne Agents they are far more independent, empowered to initiate their own missions and give rather than receive orders, working alongside (and perhaps becoming) Inquisitors rather than serving them. The whole dynamic changes. In essence, the power now available to a Throne Agent is boundless, once a situation is assessed it is up to the individuals concerned how they deal with it... and you can forget any ideas of the rule of law or due process, even though some Inquisitors like to dress up their operations with a veneer of legality. Technically, they answer only to the High Lords of Terra and the Emperor Himself, but there are many whose rank in other branches of the administration place them at a similar level, and it may be politic or expedient to treat them with respect.
Ensuing chapters focus on the Game Master, with one on how to GM at this level and the sorts of games you can run, a good collection of appropriate adversaries and finally a complete adventure, The Red Wake, to test ascended characters' mettle.
This book marks a significant advancement, both as a vehicle for characters to progress further than hitherto possible and in developing further the exposition of the setting and in particular the operation of the Inquisition. Game Masters are advised to study it well in advance of their players being ready to elevate their characters to this level, it will provide potent opportunities for them to become true movers and shakers of the 41st century.