The developer is working on Kybook 3 but it's in beta stage at the moment, here you can join in and test the beta:
http://kybook-reader.com/beta.html. I've been testing it for a month or so and it's really good. Kybook 3 is going to be available sooner or later and by the way, I use Kybook 2 as my main reader and have no problems at all.