Question: In books published by Ace Book, what is the percentage of English books published?
SQL: SELECT CAST(SUM(CASE WHEN T1.language_name = 'English' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(*) FROM book_language AS T1 INNER JOIN book AS T2 ON T1.language_id = T2.language_id INNER JOIN publisher AS T3 ON T3.publisher_id = T2.publisher_id WHERE T3.publisher_name = 'Ace Book'