Have you ever heard someone say "very unique"? Did it sound strange? Unique, which
means "the only one of its kind," is an "uncomparable adjective." It describes "an
absolute state or condition" like pregnant. Therefore, it should not be given a comparative
descriptor, which measures people and things to identify similarities and differences.
For example, unique should not have a comparative suffix such as -er or -est or be
coupled with comparative terms like more or less. It is also best not to intensify
its meaning with words like very or quite.
If something, for example a circumstance or an offer, is not unique (i.e., one of
a kind), then a more appropriate word might be exceptional, exclusive, rare, special,
The Chicago Manual of Style, 15th edition, The University of Chicago Press (2003)