I consider that genetic diversity aspects, population dynamics and their evolution perspectives are crutial for species survival and should be considered when decisions are going to be taken and priorities to be defined. The unit of evolution is the Mendelian population. The information of how populations evolve from generation to generation is more crutial than counting species per hectare!
I think that the species aspect is crutial and can be easier communicated, but is still incomplete when it is considered separately. All levels of biodiversity contribute to the general picture that a conservationist should have in mind before taking a decision about priorities, plans and activities.
It is true that most conservation initiatives taken so far globally, especially the ones taken by governments and international treaties, are influenced by the species level information only. This is one of the reasons why we win the battle and loose the war against the loss of biodiversity. I consider this book as one very nice tool, that unfortunately shows the wrong way!