And for you information, this is form American Heritage Dictionary:
For many grammarians, unique is the paradigmatic absolute term, a shibboleth that distinguishes between those who understand that such a term cannot be modified by an adverb of degree or a comparative adverb and those who do not. These grammarians would say that a thing is either unique or not unique and that it is therefore incorrect to say that something is very unique or more unique than something else. Most of the Usage Panel supports this traditional view. Eighty percent disapprove of the sentence Her designs are quite unique in today's fashions. But as the language of advertising in particular attests, unique is widely used as a synonym for worthy of being considered in a class by itself, extraordinary and if so construed it may arguably be modified. In fact, unique appears as a modified adjective in the work of many reputable writers. A travel writer states that"Chicago is no less unique an American city than New York or San Francisco," for example, and the critic Fredric Jameson writes "The great modern writers have all been defined by the invention or production of rather unique styles." Although these examples of the qualification of unique are defensible, writers should be aware that such constructions are liable to incur the censure of some readers.
