The first 7 volumes of Infinite Stratos light novel was published by Media Factory under Kadokawa. Later it was suspended, but in 2013, volume 8 was released by Overlap (under Kodansha). They in turn hired a new illustrator to redo all the covers.
Some speculate that the reason was that the author argued with fans on Twitter, giving bad publicity. If that's the case, can said tweet be found now?
Some also said that Overlap was formed by former Media Factory employees. Could the conflict be higher up?