Series Quotes
Every period of human development has had its own particular type of human conflict---its own variety of problem that, apparently, could be settled only by force. And each time, frustratingly enough, force never really settled the problem. Instead, it persisted through a series of conflicts, then vanished of itself---what's the expression---ah, yes, 'not with a bang, but a whimper,' as the economic and social environment changed. And then, new problems, and a new series of wars.
Isaac Asimov
There is one final point, the point that separates a true multivolume work from a short story, a novel, or a series. The ending of the final volume should leave the reader with the feeling that he has gone through the defining circumstances of Main Character's life. The leading character in a series can wander off into another book and a new adventure better even than this one. Main Character cannot, at the end of your multivolume work. (Or at least, it should seem so.) His life may continue,...
Gene Wolfe
If he had smiled why would he have smiled? To reflect that each one who enters imagines himself to be the first to enter whereas he is always the last term of a preceding series even if the first term of a succeeding one, each imagining himself to be first, last, only and alone whereas he is neither first nor last nor only nor alone in a series originating in and repeated to infinity.
James Joyce