3.5 stars - I wouldn't recommend you go out and read it, but it's not complete trash either.
The book covers the concept of nudges - how small changes to the way people are presented choices will change their decisions. The key point being you aren't removing the ability to choose or removing certain choices, just the way they are presented.
E.g. adding health warnings to cigarette packs or making organ donation opt-out rather than opt-in.
However the book also does a lot of pondering on the way American society could be improved by these nudges (e.g. healthcare) and even gets side tracked onto the topic of changing how marriage works.
As a non-American and non-politician, a lot of this felt irrelevant to me. The authors made good suggestions but at the same time they're just telling me things that I'm not going to be able to do anything about anyway.
It's also a bit dated. At one point the authors make a joke that women in Sweden were more likely to choose a portfolio because the authors' wives are organised (idk, some sort of stereotype about women? Felt weird to read).