Tankoubon, or better known as Graphic Novels, compile manga chapters into book format. Below you can find release date information was well as ISBN numbers to help you track down a copy of your own. ISBN numbers are for Japanese editions only.
Bunko, or pocket editions, are smaller versions of the tankoubon. They compress the series into a smaller amount of volumes to make it easier for new readers to collect. Bunko have no extras like the authors comments extra illustrations. Its just the manga, nothing more, nothing less.
The Zettai Kareshi novel titled Arigato, is a side story of the Zk gang. Written by Yura Katase and Nanawo Takahashi with illustrations by Yuu Watase. There is currently only one Zettai Kareshi novel at this time.