The Galactic Hegemony is a rather sleepy "Galactic Government" made up of 3 types of sentient beings,
- Herbivores - The most common type
- Omnivores - The second most common
- Carnivores - Rather rare.
The book opens with a survey team visiting Earth during the 15th century during which an extremely savage battle between the English and French is witnessed. The Hegemony witnesses are shocked beyond belief and it is recommended that Earth be made a protectorate of the Hegemony for it's own good.
Because interstellar travel over the vast differences is still somewhat slow, it takes around 600 earth years for the invasion and colonial government ships to arrive. The race selected to handle this are the Shongairi, a newly elevated race of carnivores with a well hidden desire to control the entire Hegemony.
The Shongairi are surprised to find not a planet locked into a medieval mindset, but a fully developed "Level 2" global civilization with all the aggressiveness of their 15th century forebearers. A "level 2" civilization is almost ready for elevation to full hegemony membership and is normally left in isolation in order to allow the final developments to occur naturally.
However, the Shongairi's political ambitions, their partial adoption of many Hegemonaic beliefs, and the complex politics of the decaying Hegemony government, cause the Shongairi to invade and conquer anyway.
They use kinetic weapons on the major cities and government centers (Drop big rocks) to kill off half the earth's population immediately. Naturally, the remaining humans kind of resent this.
This is a very interesting start to what could be a new series, but is completely derailed by a silly and forced ending, that frankly is too dopey to take seriously. Don't get me wrong this is a well written book of fiction, marred by some sort of failure in artistic judgement on the part of the writer.
I won't say what the ending is in case you want to read this book. But it would not have been difficult to rework the storyline to avoid this. And the rework I thought of even includes using many of the elements and theme he used in the silly ending he came up with.
I probably won't buy any sequel to this book if any appear unless it is VERY cheap. (Though I admit I am curious to see how Weber would dig himself out of this hole!) I bought the paper book at B&N, but it is available on Amazon.com as an ebook with no DRM. If you go there, don't read the reader reviews, as many of the respondents were so angry with the ending they foolishly gave away the ending.
Weber is normally a good SF writer, if this would be your first exposure to his work, read something else of his first. It would be unfair to let this book color your opinion of his story telling abilities.