Flimsy and poorly argued. For example, in the first chapter he cites many, many examples of white settlers in colonial America going off to live with the Indians and refusing to come back to live with their previous compatriots. Why this happened is an interesting question. But if you read Junger's quotes carefully, they equally support the explanation that the leavers valued autonomy, rather than Junger's explanation, which is that they valued community.
Pretty good; author makes some good points. But like all or most of these books, it doesn't say a thing about how to improve the lack of human connection. And that's probably not the author(s)' fault; it's beginning to look more & more like the only way to accomplish that would be to build a time machine & go back & make sure agriculture (and civilization and technology, etc.) never got invented. (You'd have to keep going back over & over though, human inventiveness being what it is. So, you know, since the only people who'd possibly have the smarts to invent a time machine love technology, don't hold your breath.)