The twenty-first volume of Vampire Hunter D has recently been released in English as a paperback by Dark Horse. You can purchase the volume from online retailers such as Amazon or Barnes and Noble. It doesn’t appear to have an ebook format available at the moment, similar to the twentieth volume.

Synopsis:

D accompanies a convoy delivering a vampire Noble to face public trial for his crimes against humanity. However, the Noble's enemies have targeted the men and women of the convoy, and they are out for vengeance! Can D bring himself to kill humans in order to protect the Noble under his charge?

The first English volume of Vampire Hunter D was released in May 2005. You can find more info on the series here on this website.