I've seen other great documents over the years. The Beowulf manuscript, Sir Gawain, the First Folio, the Magna Carta (three of them, now), various original Brontes, Austens, Dickens, Darwin, etc, etc. There's something special about standing right in front of the first copy, the book you love. To see the handwriting of John Milton or Andrew Marvel or Chaucer suddenly brings them to life, makes them actual people who lived and wrote and died, in a way few other things can. The physical process of writing - paper, ink, time, mistakes, etc. - is clearly something our culture still treasures. The wording of the Constitution has been reproduced countless times, but this document was the first one, the original, the history that must be preserved.
It's also worth remembering, in the age of saved .doc files and e-mail, that having a manuscript, whether hand written or typed out, is a solid, physical reminder that it's a book you're writing. I do keep my old print outs and notebooks, and I go back to them even years later to see what the original germ of an idea was, or whether I made a note for myself then than I can use now. Having the first ever opening line you wrote be right there in your hand is a special thing - and if that opening line gets printed and read by millions, it's even more special, isn't it?
The first time EREN appeared in one of my old notebooks (and back then it was ERIN) was many years ago, and years passed before that quick, unfinished short story turned into the book that's out there now - but still, that original, proto-EREN is special to me at least, and I'm glad I kept it. I have some earlier books, written by my 13 year old self, that I truly hope no one else ever sees - ever - but there's at least one copy of them all saved, just in case, for some reason, it's needed (And good grief, but they're bad).
So, when it comes to old writing, old stories, and old scribbles on old napkins (as long as the napkin's unused), I'm going to take a line from none other than Gandalf. And that, of course, is this:
Keep it secret, keep it safe.