Basically there was this guy on another forum who had got a copy of Revan by Drew Karpyshyn early, and he pretty much wrote most of the plot in his post, of course naturally, people didn't believe him so he posted pictures of the book and pages, it looks legit. However, too be honest, the book seems terrible, this is how the guy summarized the book.
After getting and reading a uncorrected proof of this story, pretty sure most people will think it sucks.
There are three main characters throughout: Revan, the Exile (now named Meetra Surik,) and a Sith Lord in the Emperor's service named Darth Scourge.
Revan's story is pretty simple. His dreams are bothering so he leaves his newly pregnant wife to go find out what's going on. He starts off his quest by visiting a planet the Mandolorians are on and helping Canderous find the old Mandalore's mask. Kills Canderous' wife in the process. The information he finds there leads him to the Emperor's home world, which has been stripped of life and made completely empty of the Force. Revan upon leaving is shot down by Scourge and his master and then drugged for two years so he can't do anything.
Scourge is also pretty simple. He's brought to the Imperial capital as part of a political machinations between the council right under the Emperor. He goes around doing things for them, though its pretty painful to read as he likes the tactic of bullrushing shooting enemies while hoping his armor protects him instead of blocking with his lightsaber and cutting people apart. Eventually he learns that the person he's under and a number of the people on the Dark Council are talking about betraying the Emperor because he wants to go after the Republic again. But they're all talk and don't do anything. Eventually they capture Revan and keep him captive for two years. Drugged Revan talks and does him mojo on this guy during this time, none that we actually see, and doesn't actually matter much since it doesn't come to much in the end. Except for the last bit, where he says he has a vision of escape.
Then you have the Exile, Meetra Surik. Bastila finds her and sends her after Revan. First thing you should know, is that Karpyshyn takes the game he did not write for and retcons everything interesting out of it. The Exile is a normal Jedi who was cut off from the Force and became a normal Jedi when she got it back. The Sith Lords are barely even mentioned aside from the fact that they hunted down the Jedi. Oh, Nihilus' power doesn't exist, in fact it can't exist. A big deal is made that the Emperor does the same thing and its something nobody has ever experienced before. The planet he stripped of the force to empower himself is very traumatic to Meetra, despite her in the game being the same thing. So, that part of the story of KOTOR 2 is retconned. Along with everything that came with it.
Anyway, she goes and finds this world and eventually ends up on the Imperial Capital. She finds Scourge, gets him to help her rescue Revan since he was told by him that a rescue would be coming and go and face the Emperor. Oh, Meetra is completely overwhelmed by Scourges master Sith through the use of Sith Lighting until Revan comes out and murderizes her to save the damsel. Anyway, they go face the Emperor where the three of them go face to face, until Scourge gets a vision of a different Jedi facing the Emperor. Figuring this must be the red skinned bastard's eventual killer, he stabs Meetra in the back with his lightsaber and the Emperor electrocutes Revan into submission. He locks Revan up in cryo to spend time plumbing his mind for information to help with his takeover of the Republic. Meetra's spirit refuses to join the Force and sticks with Revan to help him resist. Revan puts thoughts of caution into the Emperor's head, which is how he delays the coming invasion. The end.
I wish I was describing satire or fanfiction, but I'm not so lucky.
EDIT: In a blog post by Drew Karpyshyn on Sept 30, he mentions he knows that this person from the spacebattles forum had got the book early, and he mentioned how people started emailing him about the book, it's a good read. Here's the link. http://drewkarpyshyn.com/c/?p=302#more-302