[Quexos]

I don't know whether it can be done without removing the DRM but I can tell you that this issue is fixable if the file is epub. But you need to go into the css file and simply change the code. It must have something like "margin-left 2em, margin-right 2em (or 2px)" where 2 is a supposed value.
Then you bring that value to something inferior, down to 0 which would mean no margin which is how I like it.
As for the justify value, you need to change the "text-align justify" to text-align left. But you must be certain to find the right line of code lest you could mess other parts of the book, usually the right line falls under the tag "body" but not always. As for other formats (mobi, pdf and so on), I have no idea how the codes work)

Now as a personal opinion, I don't understand why you want to remove the full justify. Without it, the text will end unequally on the right of each line, just like this post I'm writing does. That is not nice IMO. Paper books have text fully justified and that's how I like my ebooks. But to each their own.