SELECT from multiple tables with GROUP BY

Question

I've a got a little problem with multitable query. (RDBMS: Access)

Here is the database schema: (only S_Cards, Books, Authors, Students tables are used in this query) S_Cards is Student book order (in library).

Query: Select the most popular author(s) among students and the number of this author's books, which were ordered in library.

Although I can get list of orders + authors like this in one query:

SELECT 
    Students.FirstName & " " & Students.LastName AS [Student], 
    Books.Name AS [Book], Authors.FirstName & " " & Authors.LastName AS [Author]
FROM 
    Students, 
    Books, 
    S_Cards, 
    Authors
WHERE 
    S_Cards.ID_Student = Students.ID 
AND S_Cards.ID_Book = Books.ID 
AND Books.ID_Author = Authors.ID
ORDER BY Authors.LastName

Result (sorry, it's in Russian):

I can't figure out, why I can't COUNT and GROUP BY like this:

SELECT 
    Students.FirstName & " " & Students.LastName AS [Student], 
    Books.Name AS [Book], 
    COUNT(Authors.FirstName & " " & Authors.LastName) AS [Number of books]
FROM Students, Books, S_Cards, Authors
WHERE 
    S_Cards.ID_Student = Students.ID 
AND S_Cards.ID_Book = Books.ID 
AND Books.ID_Author = Authors.ID
GROUP BY 3

I get an error that 'Authors.FirstName & " " & Authors.LastName' is not a part of static function or group.

Questions:

1. Is there a way to do this query without JOIN, only by GROUP BY, SELECT, UNION and how?
2. What's the problem in my 2nd query?

Answer 1

Solution (extracted from older revision in question):

SELECT TOP 1 Author, COUNT(Book) AS [Number of books] FROM
(
    SELECT 
        Students.FirstName & " " & Students.LastName AS [Student], 
        Books.Name AS [Book], 
        Authors.FirstName & " " & Authors.LastName AS [Author]
    FROM 
        Students, 
        Books, 
        S_Cards, 
        Authors
    WHERE 
        S_Cards.ID_Student = Students.ID AND
        S_Cards.ID_Book = Books.ID AND
        Books.ID_Author = Authors.ID
    ORDER BY Authors.LastName
)
GROUP BY Author
ORDER BY 2 DESC