When Shadowrun first appeared a number of books were released that dealt with various aspects of the setting. Virtual Realities deals with the matrix. A part of me wondered why I even got this book because I never actually used the matrix in any of my games, and when I did, it would end up alienating all of the other players who could not enter the matrix. There was a similar problem with regards to the astral plane, namely that unless you were a mage, your character could not access it, and any adventuring in there would end up leaving the rest of the party sitting around twiddling their thumbs.
I suspect that the main reason I got this book though was because of the really cool cover, and a part of me would have loved to have seen a movie containing scenes like the cover on this book. Mind you, they did have a movie like that around that time called 'The Lawnmower Man'. I still have that movie, though I am not sure if it is in my get rid of pile or if it is in my keep pile (it's in my 'get rid of, taking up too much space, pile). It is a pretty good movie, but I have watched it so many times that parts of it begin to annoy me.
One of my friends who ran a long running Shadowrun game did have a good way of using the matrix and the astral plane, and that was to try to restrict its use significantly. Mind you, none of the players actually played a decker (and from my memory not many of my players played deckers either – by the way decker is Shadowrun talk for hacker – namely because they tended to be pretty useless unless they were in the matrix). What my friend did though was to have NPC deckers that did all of that stuff. I played a Messianic Jewish magician who later on in the game was corrupted with power and became a practising member of the Kabbalah. He did go into the astral plane, but not enough to ruin the game for the others.
This book is divided into two parts. The first section deals with various rules for deckers, including their decks (portable computers that they plug into their head and then into the matrix, in Shadowrun you don't use computers by using keyboards, you use computers by thinking), the various programs that deckers can use, and rules relating to the matrix. However, as I mentioned, we never actually used this book because the matrix was so complicated that it pretty much slowed the entire game down. The second part of the book was a short story, however I cannot remember anything about the short story other than that it was about an artificial intelligence trapped in a computer system.