For example, "Of Mice and Men" Why don't they just say "Mice and Men"? Does "Of" here have any meaning? I know they do that is some recent books, too.
Here, "of" is similar to "about". They both introduce the topic of the book, conversation, etc.
"This is a story of mice and men."
"This is a story about mice and men."
"Of" isn't used this way very often now, but you still might hear a "discussion of something" (the topic of the discussion), or as a commenter mentioned, some things might be "of interest" (they are part of the current interest/topic). Earlier in history, though, it was a bit more common, and often used in book titles to tell the reader what the topic of the book was.