Return authors who have written more than one book, with their book count and average rating across those books. Group by the author, filter groups after aggregation, and order by count descending.
Expected: 2 rows. Georgi Gospodinov has 3 books and an average rating of 4.43; Yoko Tawada has 2 books and an average rating of 4.50. Do not let the two ratings for The Seven Moons of Maali Almeida inflate the book count.