This is the 605th most frequent Portuguese word.
único
Unique; only; one of a kind.
In this sentence, "único" is used as an adjective meaning "only" to signify that there is no other book read.
Este é o único livro que li este ano.
This is the only book I read this year.
Here, "único" serves as an adjective meaning "unique," highlighting the artist's distinctiveness.
Ele é um artista único em seu estilo.
He is a unique artist in his style.
In this case, "única" also means "unique," emphasizing the special and rare nature of the opportunity.