I found this tid bit of information and although it's very simple, it's also very effective and something that many writers may not have considered. This type of word usage can make a piece of writing very redundant so it's best to omit it.
The word "unique" means "one of a kind." There can only be one of that kind. This is an either/or situation; either something is unique or it isn't. It can't be more or less.
That means something can not be very unique or something can not be more unique than something else. It's like being pregnant; either you are or you are not; you can't be just a more or less pregnant than Isobel.