The Hugo award allows for a book to be reconsidered if the book has been substantially changed or amended from a previous version that was somehow flawed.  There are a couple cases of this that I'm aware of.  Moon and Dune.  You'll see Dune was nominated in '64 (listed as the original title "Dune World" ) and '65, which it won.

In both cases the initial nomination was for the serialized version:  Dune from Analog and Moon from If.  When they were later published in book form they were both revised and expanded and thus counted as different books.  I read somewhere that back in the day getting a nomination for the Hugo as a serial was often the catalyst for printing as a novel. The publisher knew they had a sure thing at that point.