Have you ever heard of this and if you came across one, would you buy it?

I have heard of this. The older the journal the better. I've seen some videos of people showing their latest finds and talking about what is written in the journals. If a person is fully identified in the journal, then there is a whole deep dive into whatever records can be found about their life and in most cases deaths. I can see the attraction of stepping back in time and being a time traveling fly on the wall of a person's life, but it also feels odd since they are not around to give me permission to read their personal and private thoughts.