I agree with the authors' argument that our knowledge of how to actually live in, as opposed to visit, space is seriously lacking. The current generation of space nerds (like Musk) tend to focus on transportation systems and neglect equally important "soft" disciplines like ecology (e.g. how to build CELSS[0]) and sociology (e.g. how to build a culture willing to maintain life support systems for generations).

However, I disagree with their assertions that international law will be a significant hinderance to space colonization. The Outer Space Treaty[1] and similar arrangements are basically modern-day equivalents to the Treaty of Tordesillas[2]; they will be ignored or "creatively reinterpreted" the moment that someone sees something to gain. The Artemis Accords[3] are already arguably an example of the latter. To quote Francis I of France: "The sun shines for me as it does for others. I would very much like to see the clause of Adam's will by which I should be denied my share of the world."

  [0] https://en.wikipedia.org/wiki/Controlled_ecological_life-support_system
  [1] https://en.wikipedia.org/wiki/Outer_Space_Treaty
  [2] https://en.wikipedia.org/wiki/Treaty_of_Tordesillas
  [3] https://en.wikipedia.org/wiki/Artemis_Accords