Our current book is Living Life Inside the Lines: Tales from the Golden Age of Animation, (public library) by Martha Sigall. As a painter and later an inker, she moved from studio to studio easily and worked for virtually everyone but Disney (although she would work on their cells when Disney needed to farm their work out to other studios to meet a deadline).
Martha offers an unparalleled overview of the day-to-day life in the studios, and of the animators in their working lives. She saw the gags and stunts they played on one another in the job, and partied with them after the workday ended. She describes the working conditions, office romances, work strikes that lead to unions, studio parties and so on. She describes how one assistant animator doubled his salary very so often by raffling his paycheck, selling twice as many chances as its worth. We meet the animators and characters they created, and understand the personalities of the individual studios.
Martha started in 1932 (when all of her paints were grayscale), and retired in 1989, offering a 53-year history of the industry from the bottom up. Well worth a read, if for nothing else, to understand how office politics have changed in the animation industry.