Elliot's goal appears to "[supply] a radically new perspective on the formative period of the modern Chinese nation," as stated on the inside flap of the book itself. The book is meant to grant new insight into how the Manchus managed to conquer and then rule over the Han Chinese for centuries, and the steps taken by the Manchu to continue this imperial rule, in terms of culture, language, ethnicity etc. It also looks at the gradual change from empire to nation over the course of Qing rule, as China and the rest of the world in the nineteenth and twentieth century saw great changes in terms of governance of countries.
Elliot seeks to approach these questions from a Manchu perspective. (Although there's a separate question in regards to sources, it's important to mention that this is a book using original Manchu sources in order to further understand the situation as it developed, hoping that the usage of these sources can provide further insight you wouldn't normally get from other (and often secondary) sources.