as there is only one relation that has a primary key with only one attribute, so we can derive only one functional dependency that is :
Book_id->Book_id, Subject_Category_of_book, Name_of_Author, Nationality_of_Author.
and here the LHS is a superkey so, it is in BCNF.
But when the attributes Book_title and Author_address are added to the relation, and the primary key is changed to {Name_of_Author,Book_title}.
We get an additional functional dependency which is:
Name_of_Author,Book_title-> Book_id, Subject_Category_of_book, Name_of_Author, Nationality_of_Author,Name_of_Author,Book_title
and we already have :
Book_id->Book_id, Subject_Category_of_book, Name_of_Author, Nationality_of_Author.
that is a non prime attribute is determining some non prime atrributes.
So, it is in 1NF(Because there is partial dependency in 1st fd).