Re: Whole or Part
I'm going to be slightly different here....
It depends on how the series was written. If (as with Howard's Hyborian Age tales, or Moorcock's Elric, etc.) they were not written in series-chronological order, then I can enjoy reading them in either fashion -- as they were written or within the chronology of the series. This is, in part, because I enjoy seeing how a writer develops his/her ideas and grows as a writer, as well as enjoying the series as a separate entity. It's an entirely different matter if the series was actually conceived/written in order as a whole to begin with, of course.
It is also a different matter with those where the writer has gone back and revised the earlier works to make them more consistent (both in tone, quality, and incident) with later pieces in the series -- unless I have both versions, in which case, again, I can enjoy it both ways.
Why have both versions? Well, because some of the best writers are writers of the idée fixe, and in many ways rewrite the same tale or deal with the same themes over and over, though with such growth, change, and extensive development that the connections are at times almost unrecognizable. And sometimes it's quite fascinating to compare the versions and see how the writer's emphasis changes from one version to the next, often completely altering the feel and implications of the tale itself (and no few times the actual incidents, for that matter -- "The Jade Man's Eyes" by Moorcock being an excellent example, where all these are greatly changed).
So... with me, it all depends on the series, or the writer....