This book by Sam Quinones is a sequel to Dreamland in the way that a history of Weimar Germany is a sequel to a history of The Great War. It was not intended, no plot threads were left intentionally dangling. But the perpetual nature of history ("Nothing ever ends," in the words of Dr. Manhattan) means the story continued anyway.
However, this time, Quinones clearly has two purposes: to inform as well as to encourage.