Having been involve for many years in the issue of "invasive" plants this was an enlightening book. I had, until recently, pretty much been in the "invasives are bad" camp. But, having read this and several other books that take a different view I have moved to a much more plant (and animal) geography point of view. With global warming we are going to have to really rethink this whole issue.
Thompson gives a professional, and maybe too professional rebuttal to widespread beliefs about the danger of invasive life forms. He takes apart the data behind commonly cited studies on "foreign" creatures, showing that the damage assessments usually fail to consider any benefits that migrating plants or animals may bring. While at it, he questions the whole basis for classifying the world's plants and animals into "native" or "foreign" categories, basically by making detailed investigations of where and when various species have appeared over the course of environmental history. Overall, Thompson keeps his challenge to inter-species prejudice dry and scientific.