What should I read in my free time as I prepare for interviews?
This might seem like a simplistic question but not for this industry. For another industry, the answer is usually to read What Color Is My Parachute and maybe a book about interviewing or the workplace. But if you want to work in book publishing, you should expect "What have you read lately?" to be an interview question and it's not a gimme question at all. It's a very important question.
The most important thing you can be doing before it's time for applying, is reading. Read a lot. Read widely. And read recently. I know, as a college student it can be hard to know what's recent and good to read. Go to your local bookstore and your local library. Look at the display tables up front, or the library usually has a whole section for recent books. Talk to someone. I know, you're an introvert. This industry is filled with them. But you've got to become comfortable talking about books with other book people. Explain the problem, and they'll be thrilled to help, trust me! Any librarian or bookseller can stock you up. Try to read 2017 books. I know, it's only February. But I've already read four 2017 books. (And I read four 2017 books last year but no one expects you to do that!) Join Goodreads and check out their lists of recommended new releases.
Read a few books you wouldn't normally. You've been reading 99% classics for the last 16 years. You will be asked, and it's helpful for you to know, what kinds of books you like. Classics isn't a genre you can work in (they've all already been published). It's hard for you to know if you like and can work with romances, sci-fi, business books, or political books, if you haven't read any. If you go into an interview saying you only like literary fiction, that doesn't indicate much contemporary reading, much stretching yourself, or much willingness to try new things. Everyone likes literary fiction. You're also setting yourself up for a bigger pool of applicants to compete with at the literary imprints. However, not as many of your competition will be applying for jobs at romance publishers or business book publishers.
While you're reading this book, do think critically about them. You might even want to write a review on a website like Goodreads or Amazon in order to get some practice. Even if you dislike a book, you ought to be thinking, who would like this? Who is the audience for this book? How could I sell it to them? Every job in publishing (except production) is selling. As an editor, you have to sell this book to your boss to persuade her to approve you the funds to buy it. Later in the process you will write the description in the catalog that the sales force will use to sell your book to retailers and libraries. If publicity you'll be figuring out how to pitch the book to reviewers. In marketing, you'll be figuring what will help get the attention of booksellers and readers. Obviously, in sales, and as a bookseller, the selling part is obvious. In publishing, you will at some point have to work on some books you don't like, but everyone has their individual taste, and it's important that you know how to sell a book you personally don't especially like.
If your focus is on editorial jobs, keep in mind that as part of the interviewing process, you might be given a manuscript to read and come back to the interviewer with a reader's report. It's important that you not focus on plot at all. It's good practice to try a few of these on books you're reading. Every book could use some tweaks or improvements (or simply editorial choices you'd do differently.) Think about the market and the end reader and what changes in the development and construction of the book could lead to a better reading experience (and think big-picture; don't worry about grammar). But a reader's report should have no more than one sentence of plot description.
Pay attention to the publishers of the books you're reading. Try to read a book from each of the Big Five publishers (Penguin Random House, HarperCollins, Simon & Schuster, Hachette, and MacMillan). Go to their websites and they will show you recent books that are popular, right on their home pages. Try an audiobook. Look at children's books from the last few years.
Obviously if you get an interview with the rare benefit of a few days' lead time, specifically try to read on or two of their books immediately before the interview. You won't always have time (I've had quite a few interviews be "tomorrow.") But I've also had three days' notice and managed to read three books in that time.
And lastly, read the blog Ask A Manager. Read the comments. Read the archives. And read the book Presence by Amy Cuddy. It seriously changed the way I prepare for interviews and how I gain confidence for them. Just read, read, read. If you are destined to work in book publishing, this should be a joy, not a chore.