I'm a big fan of immigration, and of more immigration, but I was not convinced by this book. It seems to completely ignore the short term repercussions of the suggested policy, and refers almost singularly to the supposed doubling of GDP, while ignoring how this new wealth will be distributed and who would be harmed by these changes.
Of course, the book is very US centric, and only a country with such flimsy welfare and no public healthcare could make the argument made here.

I've benefited from immigration, and I believe my new home country has benefitted from my coming here, too. But it took several years of being a net receiver of welfare before I could stand on my own two feet and become a net tax payer.

Any policy that ignores this lag and remove all annual quotas on immigration will lead to a terrible tragedy of the commons situation and widespread destitution.

So, sorry, I was not at all convinced by this argument, but then, I don't think it was aimed at me anyway. Most of the argumemts were aimed at right wing opposition to immigration, and offered right wing solutions to right wing concerns, which inevitably cause new problems.