None really...
The Soft Cover and Hard Cover only have one obvious difference... the cover
The Limited Edition has a leather cover, but you miss original cover art made by Raymond Swanland. On the other hand it's numbered and you get a certificate with it.
The folio edition is supposed to be even better in quality and comes in a nice box, I'm not sure if there are any other changes, Max should know, he owns one.
The important point is that there is no variation in the contents at all
