Louv's premise is that "the current generation of young Americans" (which he describes as part of the "Third Frontier" in a rather confusing bit of historical analysis) is characterized by "at least five trends" (on pg. 19):
-a severance of the public and private mind from our food's origins
-a disappearing line between machines, humans, and other animals
-an increased intellectual understanding of our relationship with other animals
-the invasion of our cities by wild animals
-the rise of a new kind of suburban form
These are not totally new ideas, but Louv seems to be the first writer to get this information out in a widely reviewed book that is both engaging and not overly academic. Although Last Child in the Woods does have some rather poetic parts, some of the chapters are a bit repetitive and forced, and may disengage less tolerant readers.
The different trends above vary widely in how well they are explored and explained, and I wish Louv had researched the rich literature on these topics in anthropology, ethnobiology, and environmental history a bit more deeply. Instead, sociology, education, developmental studies, environmentalism, and psychology provide interesting (if not always convincing) fodder for his argument that children today are increasingly incarcerated in artificial environments, with unforeseen and undesirable results.
Now this is an assumption that I believe to be true, so it's just the evidence provided that I'm debating. The parallels between ADHD and "Nature-Deficit Disorder" (which Louv also characterizes as "cultural autism") are weak, and the argument that limited access to natural environments causes ADHD or other disorders is even weaker. The idea that nature can cure or mitigate psychological disorders is an old one that is coming into vogue again, but Louv doesn't really marshal enough data for the reader to decide if this is ecopsychobabble or the shaky but scientifically grounded beginnings of an exciting new area of research.
Where Louv really excels is in his absorbing interviews with the researchers, naturalists, and activists attempting to bring kids and dirt, rocks, plants, and animals of all kinds closer together. And in his occasionally autobiographical stories of his own children and the canyons and beaches of his southern California home range. His examination of the effects of litigation and the covenants and rules enforced by neighborhood associations and subdivisions on children's outdoor play is fascinating, as are the descriptions of green urbanism and his suggestions for changing the way we and our children live. I'm sorry there wasn't an index, but Louv's endnotes and his "Suggested Reading" are wonderful resources.