English Women's Clothing in the Nineteenth Century, by C. Willet Cunnington

This book is by far my absolute favorite for historical research; really interesting to read, including insight as to the mentality of the women in each decade throughout the 1800's.
Very detailed in everything; undergarments, hairstyles, fashion plates, popular colors, even popular trim in each section of the Victorian era. I love exactly how detailed it is about everything; it gives descriptions of different kinds of dresses, year by year, with a larger explanation every ten years to give a broader view.
The fashion plates are my favorite; I could look through this book all day! I really would love to own it sometime.