I purchased several books in the Laura Ingalls Wilder Family Series while visiting the Laura Ingalls Wilder Rocky Ridge Farm in Mansfield, Missouri, in early June, 2016. The Story of the Ingalls Family is the first in the series and the second one I read.
The book essentially discusses Laura's ancestors, parents, and siblings, including her immediate family's travels, the subject of most of her Little House books. It was particularly interesting to read about how May, Pa, Carrie, Mary, and Grace lived subsequent to the time period covered in the books. It also talks about Laura's life as an author and includes several interesting appendices, including Grace Ingalls' diary, family tree information, and family letters. To the average reader, The Story of the Ingalls Family may be a bit boring, reading like a textbook. To huge LIW fans like me and self-proclaimed "bonnet heads," it will be fascinating.
The book definitely has a specific target reader, of which I belong. It is a short book, so due to that and my interest, on a can't-put-it-down-scale of one for I couldn't even finish it to ten for I was up until the wee morning hours, I give it a nine.
Source: Anderson, William. (1973). The Story of the Ingalls Family.