[Poppa1956]

The books I've seen with full justification have had it designated in the ebook itself, so it would have those lovely straight left-right margins regardless of the reader. That is the exception, rather than the rule.
On the Nook, as with most eReaders, the user has access to changing the font style and size —just the sort of thing that wrecks havok with full justified text— so left-justified is much more common.
Nook does not handle series/collections at this time.

edit In fact, after I posted this, I realized that most of the "professionally made" ebooks I have are, indeed, fully justified. The spacing of words and letters sometimes remind me of the days I helped my father in the print shop (early 1970's), and the new computers would occasionally justify text by having the first word of a line to the far left, and the second word of the line to the far right, with about a third of the line blank in between.
We'll get there, as popularity and technology improves. Some readers, nook among them, already have a dictionary that shows syllables, pronunciation, and definition. We'll get to auto-hyphenation in time.