Write SQL query to solve given problem: How many books did David Foster Wallace write?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT COUNT(T1.title) FROM book AS T1 INNER JOIN book_author AS T2 ON T1.book_id = T2.book_id INNER JOIN author AS T3 ON T3.author_id = T2.author_id WHERE T3.author_name = 'David Foster Wallace'