The plan was for the first book in 2014 to not be about economics... but Gladwell had to include a section about the (non)effects of classroom size on test scores!
Others have said that the message of this book is pretty repetitive, but reading about various cases of "desirable difficulty" is a worthwhile way to spend (my) time.
I thoroughly enjoyed the section on parenting, and the explanation of how difficult it can be for parents when the "we cannot afford it" excuse is simply not available. The idea that a parent needs to be able to explain the difference between "what is possible" and "what is right" struck a cord.
The part on how you might want to not attend Harvard and go to some other good university instead (because too much competition with peers is demotivating) was a bit misleading, but the broader point that working at elite institutions has underappreciated downsides is well-taken.
The part on the conflict in Northern Ireland which was trying to illustrate that "well-intentioned application of power and authority will backfire" was OK, but I think it wrongly suggested that we know more about the concept of authority than we really do.