Book Within a Book

My non-fiction manuscript is a multi-chapter family history story. Using a template of traditional design for books, it should be easy to bring the manuscript into InDesign from MS Word as one long document. But the content will be different in that at the end of each chapter’s main story, I have written a separate story about what it took in the way of research effort and process to write that chapter. More than the copious endnotes at the end of the book, these chapter additions will present a personal narrative in the same way a good mystery sequentially builds a case, keeps focus, and solves certain problems. It separates the literary flow of the primary historical storyline from the secondary story that builds chapter by chapter, a book within a book if you will. With a good visual/layout treatment, a reader could choose to skip the secondary story and go directly to the next chapter.

I am looking for creative design ideas for layout. The target is a printed book, but an e-book edition may be a possibility at a later date.

What do you think? Sidebars maybe? though these would span multiple pages. Different typographic treatment? Rule or graphic embellishment to separate sections?