Most books on the Puritans treat them as heroes or villains. Underdown does a good job of showing their strengths and weaknesses. And because they were an intense and devoted people, their strengths and weaknesses will show in stark relief.
On the good side, for example, they were very charitable, and did a lot for poor relief in regard to hospitals, education, job training, etc.
On the bad (among other things) their notion of being quiet, sober, and productive led some to be fined seemingly for the offense of being too loud in general.
Where the book falls short is trying to find a way to link their strengths and weaknesses. The book also does not explore how the Puritans compare to other Christian societies, communities, movements, etc. To be fair, the author does not claim to do this, but I would like to find a book that attempted it.