Nothing was changed in the storylines of the first 5 books of the Adversary Cycle. Prose was cleaned up, milieus and technologies were updated, but the stores remain as they were. No point in buying the reissues of those if you've read the older versions. Nightworld, however, is another story. Big changes there. Don't know whether it will be a hardcover or a paperback - won't be out till 2012.
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"It means 'Ask the next question.' Ask the next question, and the one that follows that, and the one that follows that. It's the symbol of everything humanity has ever created." Theodore Sturgeon.