Ross MacDonald is the artist responsible for creating prop documents and ephemera for hundreds of movies. That includes one of the most iconic props ever put on screen- the "Book of Secrets" from the 2004 "National Treasure" film starring Nicholas Cage. I stumbled across this interview with him last night and was amazed to see it had just a handful of views. My friends, this is propmaking gold.
In particular I want to draw your attention to the section on book distressing at around the 33 minute mark. It's a great explanation of how moisture causes dirt to migrate from the outside of the page block. As the paper expands and contracts in response to humidity, migrating particulate matter and oxidation triggers the familiar edge darkening found in old tomes. You can recreate it by browning the edges of paper with a flame, but it has to be done in a very particular, precise, and limited way. If you're burning the paper you're doing it wrong.