I adore old sewing books. These tend to have much more information than contemporary books, which may be due to sewing being a serious occupation for many more women during the first half of the 20th century than it is now in our era of cheap ready made clothing. *suppressing rant on exploitation built into system of production of cheap ready made clothing and why the first world nations have this luxury as hard as I possibly can* I’m going to work on adding many links to the vintage books I have found online, but for now, just one gem:
Harriet Pepin. Modern Pattern Design. Available from Michou Loves Vintage, a gorgeous site in German. The download page is (here); Modern Pattern Design is under the expandable menu for “Schnittkonstruktion.”
Another source is (here), and yet another source is web based, through the Wayback Machine’s archived version of vintagesewing.info, a site (now unavailable) that was a rich resource of vintage sewing books. It is (here) and photos to follow are sourced from there.
It’s available for over $100 on etsy (here) if you’re into collectibles!
This book goes into incredible detail on constructing patterns from a basic sloper. To give you an idea of how well it shows pattern manipulations, here are several examples of how to modify a pattern to create various types of cowl necklines. I just did this on a jersey kimono top and it took me about an hour using a Threads Magazine tutorial. It was an involved, frustrating process. Next time, I will try one of these:
And just one more gushing fangirl inclusion. I have been messing around trying to figure out bra making for my unique figure (broad rib cage, small bust, forward shoulder, etc) since bras have ALWAYS been a problem for me. Without the context of the bodice pattern around it, the bra cups and band are a bit puzzling and easy to screw up. Enter this sense-making illustration:
Bless you, Harriet Pepin. Bless you.
a word is elegy to what it signifies 
i,too have the same breast issues. i have tried 5 different patterns. liking a bit from each one i will add it to the final pattern. i have a band now that fits and am working on getting the cup to fit. repurposing my failures is a great way to use the fabric and try try again. this project is a great way to examine how the body is made and how we can modify the patterns to fit our bodies. this is important because it’s not just the bra fitting we need to understand but the total final fit.