Flipped through and there's plenty of material to make this a worthy purchase. The hardcover does have extra material; if you need to save some cash what you loose out on are pages of storyboards and a couple pages of miscellaneous facts from Lucas on SW minutia and a guide to when certain ideas sprang up and from which draft this occured.
After having recently read The Secret History of Star Wars, i was intriged by what the 'real' "Journal of the Whills" document was going to be. Unfortuantely the presentation of the Journal is not going to help the cause, what is provided looks like a photograph of a photocopy of the handwritten line. Annoyingly many pictures of actual pages of the hand written scripts are cropped to show the pertinent quote, would rather see the whole page... but you take what you can get.
Really digging the fact that one script started out with the phrase "Deep Space", would make for a funny subtitle.
Much of the book seems to stem from an exhaustive series of interviews done by Charles Lippencott for an unpublished work, the poorly worded "Lost Interviews" through out production of the film (75-78), and hopefully Rinzler discusses how certain decisions affected the evolutionary process of the work. Maybe Hyperspace will makes these interviews available in the next few years.
The book looks great, should be a fun read.