Hello!
I'm new to this website and forum and found this post to be unanswered. Even though it's over a decade since it was posted, I wanted to give it a boost and contribute a suggestion for anyone who is looking for books and resources about vintage clothing - or really just about any topic that might interest you.
I have found that the Internet Archive is a boundless resource with an incredible number of books, magazines, newspapers, documents, images, video, sound files and even connections to library content from far flung places. For example, a quick search of the main archive returns 891 resources when I searched the phrase "vintage clothing."
https://archive.org/search?query=vintage+clothing
Btw - this is the same organization that hosts the Internet Wayback Machine and website archive where you can search and view websites that no longer appear online or old versions of active websites.
Anyhow, I've used this site to research old buttons, makers marks, old pottery marks and more. You can find and read an entire book on any topic for free, and many you can download to keep. You'll find that you need to checkout books by registering for an account, but once you do you can save your research and create your own collections.
Also, if you belong to a local library and have a library card, you can often connect to other libraries listed in the site and use their digital resources as well. Most libraries have digital cards where you can register online and get an ID number online to use instantly.
Cheers!
Sherry