Tankoubon, or better known as Graphic Novels compile manga chapters into book format. Below you can find release date information as well as ISBN numbers to help you track down a copy of your own. ISBN numbers are for Japanese editions only. Epotoransu! Mai has not been released into English.
Since the series initial release into tankoubon form, Epotoransu! Mai has been compiled into one giant manga!
Bunko, or pocket editions, are smaller versions of the Tankoubons. 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, or extra illustrations that the tankoubon have. Its just the manga, nothing more, nothing less.