Okay, so this novel takes place in an alternative Star Wars universe. Obi-Wan Kenobi is now a very aged old man. He has long since given up the mantle of Jedi after the death of his protege, Anakin Skywalker, 13 years prior. Thirteen years ago, Obi-Wan Kenobi and the Jedi Order were able to stop and intervene in Darth Sidious plans. Unfortunately, it was a pyrrhic victory. A victory that cost the life a lot of people across the galaxy including the chosen one, Anakin Skywalker, and many other great Jedi Master's. It is revealed that about three fourths of the Jedi in the Jedi Order were perished in that war. The remaining Jedi, including Obi-wan Kenobi, lose their faith in the Jedi Order. And as a result the Jedi Order gets disbanded after the war. With the fall of Jedi Order the Galactic Republic also becomes more weak and instable.
All of this results in the rise of an ultra violent cult known as the "The Divine Hand", consisting of force-senstive people who have proclaimed that force-senstive people are the dominant sentients in the universe and hence they have the right-to-rule over non force senstive people. And anyone who opposes them are outright killed. Which results in the killing, oppression and slavery of a lot of non force users across the galaxy. Note, while they know how to use the force they don't use lightsabers since they don't know how to construct one. The first half of the novel deals with Obi-Wan Kenobi eventually coming back and helping out the weakened Republic to fight against the "The Divine Hand". He is also eventually joined by other former Jedi members such as Agen Kolar, Roan Shyrne, Stass Allie, Quinlan Vos and Coleman Trebor and other new force-sensitive people who are also against "The Divine Hand". With this new sort of Jedi Force they are able to regain most of their lost systems.
The second half of the novel takes place roughly 3 years afterwards. The "The Divine Hand" cult is mostly destroyed. The surving members of the cult have surrendered and been sent to prison or are given the choice to join the new Jedi Force of the Republic to protect people. The second half of the novel mainly deals with a mysterious hooded man attacking and killing various Jedi bases and innocent people, who's face strikingly resembles that of Anakin Skywalker. It is also revealed that some of the victims were raped and tortured by him. Eventually, Obi-Wan kenobi and his other fellow Jedi members are able to locate the Jedi Killer. Obi-Wan Kenobi along with his new padwan Rachi Sitra and two other Jedi Masters, Agen Kolar and Coleman Trebor all travel to the location inorder to stop him.
It actually turns out to be trap set by the Jedi killer. As he seen waiting for them. A one versues four battle ensues. But, the Jedi Killer turns out to be too much for all four of them. The Jedi Killer reveals that he has not only mastered all the seven light saber forms but has also created 13 completely new forms. This makes him completely unpredictable and almost impossible to read his movements. In addition, his force potential seems to even eclipse whatever Anakin Skywalker showcased. Agen kolar is killed first followed by Coleman Trebor who dies while saving Rachi Sitra. Eventually, Obi-Wan Kenobi get's knocked out cold with powerful force push. Once, Obi-Wan Kenobi awakens it is revealed that the Killer raped and tortured Rachi Sitra. He even peeled her skin off. And, chops of her head once Obi-Wan wakes up. Also, Obi-Wan Kenobi movements are restricted or something like that by the Killer's force power.
The Jedi Killer eventually reveals that Obi-Wan's right that he is not Anakin Skywalker. He lowers the hood and shows his complete face to Obi-Wan. Around his face we see stiches. He then takes a knife out from his side and starts to cut his face to the horror of Obi-Wan. It is reveled that the Killer's name is Urion and was also Obi-Wan's temporary padwan for a short period of time. When Obi-Wan questions him why he is he killing the Jedi, Urion reveals his dark past to him. It is revealed that his Jedi Master use to beat him up and forced him to oral sex. Sometimes, his Jedi master would even torture him by burning his skin with the lightsaber and then force heal him. It is also revealed that the higher ups in the Jedi didn't catch on to this because Urion and his master were assigned to a Jedi outpost that was in the Outer Rim. The outpost was mainly for force user who had a very low midichlorian count, just barely touching the requirments to be trained in the Jedi ways. As a result, the outpost is more or less often overlooked and forgotten. It is also implied that he used to get bullied by the older students over there for identifying himself as a female. He eventually snaps one day during a mission with his master and kills him during the mission. His master is noted as Killed in action. It is during this time that Obi-Wan kenobi is temporarily assigned as his padwan till a new one is officially assigned. But, the war escalates and the Jedi Order becomes busy and while in the midst chaos Urion dissappears.
Urion then reveals that he is doing all this to get his revenge on the Jedi. And he used Anakin Skywalker's face, a Saintly face revered by many in the universe, just to tarnish the Jedi and the Choosen one. He also reveals that he fell in love with Obi-Wan kenobi ever since he had taken him as his padwan and showed him kindness. He then reveals his real plan. Since he is very powerful and attuned with the force he plans to create a blackhole that will kill everyone in the universe except for both of them.
That's all I could remember from the novel. I think Obi-Wan tries to escape and trap Urion in his blackhole but fails. And he almost get's killed by Urion but gets saved by Darth Maul in the end. The chapter ends with Darth maul and Obi-Wan Kenobi facing of against the now deeply demented Urion.