Throughout Mad Men, books appear that are a direct reflection of characters or the period they live in. There are books characters are reading in which, in a real meta moment, characters feature that are the templates of themselves.
Mad Men is, in essence, a period piece, and props in any period piece are essential. Viewers will turn on a show if a character glances at a digital wristwatch, is leafing through a copy of Game of Thrones or a is wearing a pair of Jordan VIs.
Just check out the list of goofs people spotted if you’re unsure. Gotta respect the how much people care. Heck, I’m one of them, so I ain’t complaining.