This is the 1045th most frequent Portuguese word.
fábio
"Fábio" is a proper noun, commonly used as a male given name in Portuguese.
This sentence refers to 'Fábio' as a proper noun, specifically as someone's name.
O Fábio sempre chega atrasado na aula.
Fábio is always late to class.
Here, 'Fábio' is used as part of a title of a book, still retaining its role as a proper noun.
Você já leu o livro 'A História de Fábio'?
Have you read the book 'The Story of Fábio'?
In this case, 'Fábio' indicates a name, implying it was one of many people with that name.