I found this book to be a good place to look for inspiration and overall themes. It doesn't get too much into the nitty-gritty, hard-working pages of ads mixed with content, but it does talk about process and consistency of voice. The author lets several editors explain the design choices they made when faced with title relaunches and updates, and how those choices reinforced the type, photography, writing style, and illustrations used. There are rationale breakdowns of section headers, feature articles, grids, typography, photographic styles, etc, for several well-maintained and respected magazines.