I initially thought that the $ indicated obscure self-published works that they sell and nobody has ever seen, as those often dominate a lot of these kinds of things, but at least two of them including
Viking Age Iceland are at least semi-legit academic works, the others are just collected essays.
Viking Age Iceland is literally what it says on the cover. I assume it drew attention because the Vikings did not exactly setup a "state" as there weren't really any at the time so things like "they had no foreign policy or standing military" is misapplying a current concept backwards. I think it's more a problem of our current IR scholars not considering "raid and rape everything in sight" as not being a valid "foreign policy" due to their bigoted cultural norms.
However one of them is most definitely this, and you'll never guess which one:
spoiler (click to show/hide)
The essays contained in this volume were the result of many years of intensive thinking and reading about liberty. They address a topic, anarchist strategy, that is underdeveloped. Many people have written about how a free society might operate. But relatively few have applied hard thinking to the key question of "What do we do to achieve that world?" In the few instances people have, their proposed solutions have always been vague (a generic call for "education") or unconvincing (defeating the state through black markets - "agorism"). This is a problem. As long as we lack a comprehensible plan to bring about a free society, we will be unable to convince people that our ideology has a future. This will make them unwilling to act on our behalf. A person acts, as Mises explained, only if he believes that by acting he will successfully remove a felt uneasiness. Until we develop a plan to beat the state, I do not think our movement will inspire the hope necessary for action. The essays in this book are an attempt to solve this problem. In them, I outline a comprehensible plan for ending the state.