The complete versions are easy to follow for the most part, bar the titles. We do have for the most part all of the major ones (including the IMO bizarre first draft). In regards to the older versions, many of them are simply half-baked story ideas or world-building things.
There was an actual Journal of the Whills at one point; a three page first-person account of a very different story (which I think could have made for a very interesting take on the prequels). From there, it was mostly scattered notes until the treatment (which is actually on that site linked earlier, and interesting because Lucas actually states this takes place in the thirty-third century, instead of long long ago).
You can find a bunch about Journal of the Whills from this thread;