Ms Somerville's writing seemed profound when I read her when I was 17 years old, but now I see the faults in her reasoning. The book uses interesting examples that keeps it fresh; however, it was irritating how the author consistently reaches conclusions by gut/instinctual feelings rather than reasoned arguments. As I went through the book it was always mysterious how the conclusions were reached, since it appeared that the author reached the conclusion first and rationalized it afterward.
Overall, this book is a good if you are a conservative Roman Catholic and want some arguments to use to hold your own for a little longer against better reasoned arguments by better ethicists.