"Dirk Moeller didn't know if he could really fart his way into a major diplomatic incident. But he was ready to find out."
That's the first sentence of John Scalzi's book "Android's Dream". The rest of chapter 1 is available for free at http://www.scalzi.com/whatever/004945.html. Go read it. It can stand alone as a short story or it can tempt you into going out to buy the whole book.
Here's the summary of the book. Mankind has gone to the stars and found hundreds of alien races. We're not the puniest race, but that's only because a few hundred have no space military at all. We have to make friends with whoever we can. That includes the Nidu. Also pretty puny, but still several hundred steps ahead of us. After the diplomatic incident in chapter 1 they're ready to conquer Earth. But there is a way to make nice.
The head of the Nidu empire has died and his heir has to follow a special ceremony in order to take the throne. Failure to do so leaves the throne open to other families. As part of the ceremony they must sacrifice a member of a rare, genetically engineered species of electric blue sheep known as "The Android's Dream" after the Phillip K Dick story "Do Androids Dream of Electric Sheep" (better known as the movie "Blade Runner". But someone has killed every last one of "The Android's Dream".
The book tells of the search for the last Android's Dream, the struggle to keep it from getting killed by either side, and the multigeneration plot to take over the Earth.
It's a great book. Go read that first chapter.