Its treatment of the Puritans is far more even-handed than you will find in most histories. It also places them firmly IN their time, in context, which is important not only when it comes to understanding Puritanism but how it affected America.
With its focus on Winthrop it only brushes upon such notables as John Cotton, Roger Williams and Anne Hutchinson (among others) but that is what is great about it, it introduces you to figures you want to know more about.
It is a brief book, a little more than 205 pages long but it makes great use of every page. There are various longer looks at the Puritans and Winthrop but few get at the man and the beliefs like this one.