I wish I'd tried the free preview with the Kindle. Then I'd have known that the author's first primary source (of the 70 or so people she claims to have interviewed) was (in)famous conspiracy theory superstar Bob Lazar. She glosses over most of his claims and outright ignores his most outlandish ones while playing him up as an authoritative source on this most secretive of places.
I'd have also noticed some of the quite bizarre and jarring factual errors/typos (claiming the CIA had no idea what the USSR was up to "west of the Volga, let alone west of the Urals" when she surely meant "east" being the most egregious example).
At this point I abandoned it as a serious work of research (try Trevor Paglens excellent book Blank Spots on the Map: The Dark Geography of the Pentagon's Secret World
if you want that). Instead I pressed on with it as a sort of techno/conspiracy thriller and actually it works really well in that genre - and as such I won't spoil the twist.
Fans of the X-Files might like this book (and people who think the X-Files is a documentary definitely will), just don't expect a serious academic work.