Testa den här frågan
SELECT book.BookName, autor.FirstName, autor.LastName, rubric.RubricName
FROM bookautor
JOIN book ON book.BookID=bookautor.BookID
JOIN autor on autor.AutorID=bookautor.AutorID
left join bookrubric on book.BookID=bookrubric.BookID
LEFT JOIN rubric ON rubric.RubricID=bookrubric.RubricID;