I have read the book cover to cover several time and used it for reference many, many times.
It's simply the best book for identifying and dating fabrics in quilts, no doubt about it! many reviews stated it was of great assistance with dating fabrics and determining quilt age, however I found the opposite to be true.
Generally, by the early 1930s narrow widths were replaced by 36″ to 39″ for most all American dressmaking cottons and by the early 60s the standard was 42″ to 44″ though some 36″ widths cottons lingered on for another decade.
One notable holdout is Liberty of London lawn still being manufactured in 36″.
Anyone who loves history and/or quilts would find it to be both a tremendous resource and a great reading experience. I can honestly say this book is the very best, most comprehensive book on dating quilts that I have read.