I found this on the Language subreddit, and while it's short and not necessarily useful, the polyglots referenced within are actually very interesting to read about. Specifically, Kató Lomb has written two books specifically about languages. Highly recommended reads.
http://www.languagecrawler.com/2015/10/five-accomplished-polyglots-youve.html?m=1
P.S.
I stand corrected. She has actually written four books. Here are direct PDF links to her two books that I was aware of:
www.tesl-ej.org/books/lomb-2nd-Ed.pdf
www.tesl-ej.org/pdf/ej66/TESL-EJ_HarmonyOfBabel.pdf
