The unique perspective of seeing life through a doll's eyes, while surveying a great sweep of history, is an interesting concept and an enjoyable way for a child to grasp some of the changes occurring over that time span. The writing quality is high, as one would expect from a Newbery award winner.
Some people take some comments (see examples in Noteworth Issues) as anti-Christian. Others see them merely as comments on individual situations; the verses and hymns didn't do one little girl much good because she was sent away from her parents and her nurse didn't discipline her, for example.
There is less than stellar behavior by some of the children who own Hitty and a few values that you might not want to pass on to your child (the desire to be fashionable, for instance). This is not a particular favorite of mine, but many will want to read Hitty: Her First Hundred Years because it is a Newbery Award winner. In that case, consider reading it aloud, editing as best suits your family.