The book has a lot that is of interest only to scholars, and much that is of interest only to scholars in her field, but there is a lot that is useful to everyone. I think lefties can particularly benefit because she provides empirical research to show that a lot things we tend to do will not actually help (she isn’t alone in her claims about that–she pulls together a lot of research).
The empirical research, like hers, is clear that Americans agree on policy, especially policies that would imply higher taxes for the wealthy, reasonable gun control, government-funded healthcare, and various other progressive policies. But running candidates who advocate those policies won’t work because people (including a lot of lefties) vote on the basis of partisan identification.
They cheerfully (sometimes without knowing, sometimes completely aware) vote for political figures who will enact policies they don’t want, but they do it because their side winning is more important than any policy issue.
The more people identify with a political group–the more all their various group identifications align with a political party–the more they engage in motivated reasoning. People with cross-cutting identities are more likely to engage in empathy with other groups, advocate tolerance, and be willing to argue about policy.
This is a complicated point I won’t make here, but I think her book helped me understand the very specific ways that GOP trolls and clickbait fractured the left (and are already doing so today, especially in regard to AOC). Here are some of my favorite passages.
