Almost every marina or place where cruisers gather have a library full of "take and give" books. Books are also brought to potlucks, etc.
Often times we have seen other cruiser's names, boat
, etc written in them. Kind of gives them some history
like you suggest.
The other things that give these exchange books history are the mold
and mildew, bad smell, cockroaches eggs, small "book bugs" (I don't know what these are called), and lots of other gross things.
More and more, people are exchanging whole digital libraries of ebooks. We pretty much refuse to take on board real books anymore.
Be aware of one thing about book exchanges - if you don't like serial
detective novels, romance novels and all the other crap mass produced today, you will find the pickings extremely thin to non-existant. If you bring other types of books to be offered, you will most likely see them still there next time you come around.