There have been two updates after I wrote the review below and two column display has not been added. I am still hopeful.
I still love this ebook app. However, I just bought a new iPad Air and prefer a two column display in landscape on the iPad. Other readers support this but Shubook does not.
I am not abandoning Shubook because its other features are still heads above the others but I would be much happier if this change could be made.
When this happens I will restore my five star rating.
Bermuda Bill about ShuBook 1F