Just what it says on the cover -- a history of the space advocacy movement during the 1972-1984 period. I was a member of the L-5 society and the Space Studies Institute as a student in the 1979-80 era, and much later in life (starting in the mid 1990's) become very actively involved in citizen advocacy for space and later directly involved in space entrepreneurship. So I had come to know most of the history recounted in this book by conversation with the participants. Still there were pieces I didn't know, and the pieces I did know line up pretty well with the author's treatment and description of them.
I think the book deserves wider attention today, as the up-and-coming generation of space enthusiasts who have come of age in an era of private space are going to encounter many of the same challenges and there are lessons to be learned from the early days.
It would be interesting to have someone write a period of the rise of the commercial space enterprise, as well, which would dovetail with this nicely (the tail end of this book covers some of the early private space ventures), accelerated rapidly in the mid 1990's, and broke out in to the public consciousness with the X-Prize and the rise of SpaceX and Blue Origin; but that is a work for future authors.