I bought it and was a little disappointed. Don't get me wrong, if you haven't got the original "Book of the Alien" then this is a great buy. Its a good quality ,slided-in boxed hardback with envelopes that have extra items, such as prints of the space jockey, plans of the Nostromo, storyboards etc which are a nice touch.
Unfortunately I found myself comparing it with "The Book of Alien" which has ( unsurprisingly) much of the same content but scores by having more of the artwork , set designs and arguably much better photos, particularly of the models and creatures. I was also disappointed that the ALIEN itself is perhaps less well photographed here than in the original book, and there are threads out there ( Space 1999 Eagle Forum) that have far better pics and more interesting content than can be found in the Vault.
It also pulls an awful lot off the DVD's "making" of documentaries, almost story by story. It also illustrates just how many rewrites took place before the script became what it did and the bitterness that was generated between people, particularly from O'Bannon, for key additions to the story by others that really did help improve it.
I also have to admire Ridley Scott for sticking to his guns and (bravely for a first time director)fighting the studios all the way to get his vision filmed, as they were dead set against Giger,some of the key scenes and set spending overall. Again you do get the feeling from the book just how valuable it was to have such a creatively talented team assembled that really helped refine the final product into being such a SUPERB film. Ridley Scott listened, kept and threw away what didn't work and did the directors job properly.
Although there is nothing much new to the story of the filming or its mythology, this book really does give you a feel for how hard a scrap it was to elevate it into becoming the classic it is today.
There are also no real clues as to the true origin of the Alien , other than you get a pretty clear idea they wanted to take it in certain directions but couldn't afford it and were then happy to let all the alternatives die off and remain an unexplained mystery. I believe the prequel will be heavily influenced by the "excised" temple/life story though, as Ridley was very keen to get that in the first film, if he could have afforded it.
So, its a very nice book to have, but in the thirty odd years since it came out it can't really add much to the history of the film that hasn't been written about and documented before.