I have "The Making of The Empire Strikes Back" by J.W. Rinzler. It's officially licensed and is 372 pages long. Given the fact that the "Alien" franchise and fan base is not as large as that of Star Wars, I'd imagine that this is the best we are going to get in terms of an officially licensed "Making of" about Scott's film.
I just hope that most of the cast and crew were, in one way or another, participants in the information in this book. I was really annoyed that Yaphet Kotto was nowhere to be seen in the interviews for the Quadrilogy Box Set.