Kvinnligt mode under två sekel by Britta Hammar and Pernilla Rasmussen (the same people who wrote Underkläder: En kulturhistoria) is the best and most informative book on 18th century fashion that I’ve read. It only exists in Swedish as far as I know and it covers women’s fashion in the 18th and 19th centuries.
The first section is a general history of fashion, with many pictures and fashion plates. The second part has examples of garments (from the collection of Kulturen in Lund) presented in great detail with photos and thorough information on the construction of each garment. The final part of the book contains many examples of different sewing methods and stitches used in clothing from these two centuries, and finally there are patterns of every garment presented in the book!
The only bad thing about this book is that it seems impossible to buy. I borrowed it at the library but I can’t find it for sale anywhere. If anyone knows where you can find it please let me know!