Here’s a little behind-the-scenes publishing info. Photo insert placement is one of the hundreds of odd little decisions I make as a book’s editor. Books aren’t simply a bound-up stack of single pages; they’re a bound-up stack of little booklets; each little booklet, called a signature, is a folded group of a certain number of pages. The number of pages per signature can be 16, 32, or 48 (or others, but these are what I deal with the most).
When a book has a photo insert, that special signature of glossy paper gets placed between the regular text signatures. At some point, a person from production will come to see me and say something like, “Where do you want the insert? The best breaks are at pages 138/139 and 234/235.” The page numbers might not match what you would expect from the signature size if the book has front matter paginated with roman numerals.
The preferred placement for an insert is usually near the middle of the book, but it’s also nice if it doesn’t break a sentence, that is if the last signature before the insert ends with a complete sentence instead of in the middle of a sentence that’s concluded after the insert. It doesn’t always work out this way. Sometimes the only clean signature break is on, say, page 48 of a 336 page book, and it would just look weird having the insert that close to the front of the book.
Under those circumstances, I’ll pick the signature break closest to the middle, but with some more preferences involved. If I have to break a sentence, fine, but I wouldn’t want to interrupt a hyphenated word. That just seems rude somehow. These are the kinds of esoteric aesthetic decisions that go into making a book. I think they help, at least subliminally, the end experience for the reader by providing a nice flow while reading.