I realize this is not really a good description of the book. The Amazon short review describes what the basics are, but there is a lot more to this book. It's one of those subtle works that makes you think about what you believe in and how you see yourself.
It is a lovely book, by turns funny, sad, touching and thoughful. On the surface it deals with salmon and challenge of bringing them to Yemen. On a deeper level it is about faith, but not necessarily about 'church-type' faith. It is more a question of what you believe to be true or possible and why can't one dream a little. Just because everyone says something can't be done, isn't there a slim chance that maybe it could? It is also about people and their perceptions of the world and themselves. One of the characters ends up totally reassesing his life because he is willing to believe in the impossible, another precipitates a disaster because he thinks he can bend everything to his perception. And then there's the sheik.
In short, read the book. I think you'll like it even if you don't know beans about Yemen or salmon, or even British politics. I didn't and I loved it.