@kafkareich,
kafkareich wrote:Would you say "Look inside p.55" when referring to something inserted in between the pages? Or "Look inside at p.55"
If you mean something inserted in a book, between the pages, such as a piece of paper, a photograph, postcard, pressed flower, etc, then you could say "look in [book title] between (or in between) pages 54 and 55". Note that by convention, each even numbered page (each "verso" page) is on the same piece of paper as the preceding odd numbered page (or "recto" page) so that nothing can be inserted between an odd numbered page and the following even numbered page.