One would think that Hawkins, who was a full professor and chairman of the Astronomy department at Boston University from the late 50's, would not be the typical 70's loon ... but it appears that the work he was most interested in (i.e. Stonehenge as a computer) fed in so well with the particular "pseudoscience zeitgeist" current that one has a sense that he got swept away in that movement.
This book is, arguably (although not specifically), in three parts. The first third of it, chapters 1-5, deals primarily with Stonehenge, and the author (being "an expert" with all this computer backup) getting tapped for a TV documentary on the site. In this section he describes his work there, the numbers involved, other theories, various techniques (stereo cameras, etc.) used to try to find new data, and an updated plan of the ruins that they were developing. So far, so good. A bit "quaint" technologically, but pretty straight forward, and an interesting "window in time" to the 60's efforts in "archaeoastronomy".
The next half of the book, chapters 6-12, do follow logically from the first part, in that Hawkins appears to have been in reasonably great demand as a "guy who can put science into this stuff", and he (and whatever input device he was using to get raw numbers back to the mainframe in Boston) was being dragged off all over the place. First stop (again, for a TV project) was the Nazca Lines. It's easy to forget how recently the figures on the Nazca plain have come into international consciousness. Von Daniken did not publish the first of his "space alien" books until the late 60's, and here Hawkins has the lines presented to him as something "completely new" that the TV guys wanted him to analyze for "astronomical alignments". I suppose we can forgive some of Hawkins' "ooh, wow!" moments (my first visit to Peru was filled with enough of those, even having read extensively of the sights before going), and to his credit he pretty much shows that the lines were not a calendar or observatory (what "alignments" there were rated no better than "chance"). However, this was not the end of it, in this section he's off for Cuzco and Machu Picchu, looks at the Nazca culture as "lost civilization", talks about Heyerdahl's Kon-Tiki work, looks at Tiahuanaco, analyzes alignments in various Mound Builder sites in the U.S. Midwest (including the "woodhenge" at Cahokia), considers a few Mayan sites, and then, somewhat back-tracking from Heyerdahl's Ra (based on similarities of boats on Lake Titicaca), ends up in Luxor to see how the ancient Egyptians were doing on astrological architectural alignments. One gets the sense of "breathless adventure", but of a sort more fitting a clueless TV producer than the chair of a university's Astronomy department.
It's in the last "section", chapters 13 & 14, that Hawkins "goes off the deep end" and launches into one of those oh-so-70's rants about the end of civilization. To those of you who think that Al Gore invented "OMG, WE'RE ALL GONNA DIE!" environmental alarmism, it was worse in the early 70's, with predictions (quoted in the book) that we can expect "the irreversible disruption of the life-support systems on this planet" resulting in "a lifeless world" "by about A.D. 2000"! One almost gets the sense that Hawkins was "playing to" the undergraduates of 1973, pumping up the book with "trendy" doom-and-gloom and citing assorted then-popular nutcases so off-the-edge that they make Mr. Gore and his cronies look nearly sane.
So, there you have it ... a book that starts off quaint and ends up blithering. From a perspective 35 years down the road, the main take-away is "this guy needs his meds adjusted", despite there being quite a lot of "interesting" bits in the text. Again, the first third is worthwhile reading, the rest, well ... you've been warned.
Remarkably (or not, given how well other "delusional" books sell), this is still in print in a 2001 paperback edition. The 1973 hardcover I have, however, can be had from the Amazon new/used vendors for as little as 1¢ (plus $3.99 shipping, of course) for a "good" copy, and you certainly wouldn't want to spend more for this than that. By the way, the 2001 edition is 59 pages shorter than the 1973 edition ... I wonder how much of what parts got cut out (the "third section" is only 33 pages, so they may have started there)!