Spoilers for the Kamen Rider Ryuki novel has surfaced online and just like most Kamen Rider novels, this take place in an alternate universe. The novel was released last August 30 and written by Toshiki Inoue and Naohiro Okamura, with Inoue as the editor for the novels.
Ryuki, Knight, Zolda, Ouja and Femme are the main Riders. Imperer, Raia and Scissors are mentioned but die literally immediately and their human forms are unnamed. Shinji kills Imperer in the novel and doesn't regret it. Shinji is a jack of all trades, Ren and Yui are friends with benefits. Even if that is the case, he is still with Eri. Kitaoka has Alzheimer's disease while his "butler", Goro has his mouth sown shut with a golden wire and can't speak.
Unlike the original TV series and movies, they don't use cards to transform. They transform with an emblem in front of a mirror and jump straight into the Mirror World. Apart from everything is mirrored, there is no sound in the Mirror World. In the novel, they are not called Masked Riders, but instead they are called Masked Contractors. Asakura is said to be the embodiment of your standard Toshiki Inoue written jerks.
Just like in the movie, Femme asked Shinji to pretend to be her boyfriend, they end up dating for real and have sex. Lastly, the novel still follows the same Battle Royale struture with the ending nearly identical to the TV series.
[Source: DecaEnd of HJU]