You’ve mentioned three great ones already (I particularly love Jean’s writing style—her columns for ELLE magazine in the 90s were one of the reasons I gravitated towards magazines, and beauty, at all). I would also look into Diana Vreeland’s memoirs, The Teen Vogue Handbook (not just saying that because I worked on the book. It gives a great baseline knowledge of the different careers in fashion, from art department to designer), and—this may seem random—The Mailroom. The latter is a book about working in the mailroom (basically as an assistant) at top talent agencies (CAA, William Morris, UTA) in the 80s and 90s. It may seem like an utter disconnect but when I read the book, I saw a lot of parallels in what it takes to make it as an agent as it does an editor: the same drive, ambition, organizational skills (truth!). Lastly, I would encourage you to be informed about the world as the whole, not just the fashion world. It’s important to be attuned to current events, local issues, and culture—you can live for fashion, but remember that you live in a larger community that informs fashion. Make yourself as well-rounded as possible. (And to answer your last question: yes, it is in the works ^_^)
Personal style: it sounds (and looks) so simple yet it’s an elusive, tricky thing to nail down. Because, really, at the end of the day it’s personal. There are some people who find their so-called personal style and are self-assured of it from an early age; others, it might take high school, college, twenties, thirties. Really, though, I think personal style is less about a signature look and more about the confidence to wear what you want to wear. Sounds simpler than it actually is, though, right? So, where to begin… I would start by incorporating some fashion items (maybe it’s a pair of boyfriend jeans, penny loafers, overalls) that you love but are somewhat unsure of. The more things you try on and say, “Oh, hey, I loved that! I want to wear it again” or “I didn’t feel comfortable in that”, the better. Personal style is trial and error and, most importantly, ever-changing. Enjoy the evolution—don’t over-think it or worry too much about it. Fashion should be fun, an outlet, not a burden.