1. His history of change 1870 - 2015 is good. Some weaknesses, but solid, and he makes his case for dramatic changes. A mention of Maslow's Hierarchy of Needs would improve the discussion, but his point even without stating that is of drastic changes (and improvements) to basic food, shelter, clothing, and security needs.
2. He misses some infrastructure with his focus on consumer impacts. Less so with early work than in his discussion of information and communications infrastructure, in which I think there might be some weaknesses to his argument (and a possible out for the optimists).
3. You'll find the meat of his theory in the third section of the book. Chapters 15-17 IIRC. Focus your critical eye there.
I've got many quibbles with his economics arguments, though most of the errors actually bolster his overall argument -- I feel actual recent trends are worse than Gordon states.
Steinbeck's Grapes is a true classic. Reading that as a story of an epic animal migration (as Steinbeck begins it) is humbling.