The Ends of the Matrix is a set of full replacement rules for the Matrix of Shadowrun 4e. That means that these rules are intended to be used instead of the Wireless World chapter (SR4, pgs. 206 - 240) and instead of the Unwired book (all pages). It is not a full replacement of the Shadowrun world story, so books like Emergence and System Failure stand on their own. This piece is admittedly quite long, but when you factor the number of pages of material that it replaces, it's not that bad.
This work is different in tone from other Shadowrun books, because the flavor text is not written "in character". This book is written with a voice directed at the players of the game, and with good reason. The matrix is an integral part of the lives of every character in the game world from birth, and it really isn't reasonable to expect to find material that the characters would consent to read that wouldn't make assumptions about basic levels of matrix familiarity that the players doubtlessly do not have (not living in that world). While astral space is something that a majority of characters in the 2070s have never experienced, matrix interaction really isn't. In addition, this is a set of optional replacement rules, so the author has chosen to break the 4th wall constantly in an effort to show the reader both how the system works and why it works that way instead of some other way. After all, the Matrix subsystem has undergone an almost complete overwrite upwards of 9 times already (SR1, Virtual Realities, SR2, VR 2.0, SR3, Matrix 3, Target: Matrix, SR4, Unwired), so it seems clear that the number of ways that the Matrix can be conceived of and modeled in-game is tremendously large. Justifying the model here is probably necessary.
The question is raised however of "why do this at all?", and the answer is because I honestly am not happy with the Matrix rules as they stand, and do not believe that they hold up to careful observation. The first insult thrown at anyone who complains about rules (or any intellectual property) is along the lines of "If you don't like it, why don't you make something better?" Well, hopefully I have. And while I lack access to a large playtesting crew, I don't think there are presently any giant holes in this rule set. If there are, then that will be a shame, and I will humbly accept my plate of delicious crow.
So what precisely is wrong with the Matrix rules in SR4 such that they need to be completely rewritten from the ground up? Again, for the 10th time? Simply: the Matrix rules in SR4 do not hold up when people attempt to push them or exploit them. Even authors of Unwired have described it as "Six parts Hollywood hackers, six parts modern tech, zero parts playtesting by a powermunchkin", and that's a shame. Fundamentally, I believe that the matrix rules need to be more solid than do the rules of other subsystems. Unlike magic or car driving or whatever, the Matrix is predicated on the idea of the acting characters actually knowing the rules and deliberately attempting to exploit holes in them. Hacking is about finding power exploits, so if power exploits exist in the rules it is actually counter-immersive for characters in the world to not use them.
So the basic SR4 rules contain the exploits of
The net result is that characters with no technical skills at all can throw some money on the table and hack as if they were dozens or hundreds of hackers at no actual risk to themselves or anything they care about. That's bad, because the entire concept of a hacker entails the fact that if they could do that then they would. It is the hope that these presented rules will not have problems like that, or that if they do that at the very least they will not produce a such perfect storm which relegates the concept of the Matrix Specialist to the dustbin of history.