Why do they add "of" at the beginning of titles in old literature?

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.