Article: After completing filming on Ready Player One, while it is in its lengthy, effects-heavy post-production, he will film his long-planned adaptation of David Kertzer's acclaimed The Kidnapping of Edgardo Mortara. The book follows the true story of a young Jewish boy in 1858 Italy who was secretly baptized by a family servant and then kidnapped from his family by the Papal States, where he was raised and trained as a priest, causing international outrage and becoming a media sensation. First announced in 2014, the book has been adapted by Tony Kushner and the film will again star Mark Rylance, as Pope Pius IX. It will be filmed in early 2017 for release at the end of that year, before Ready Player One is completed and released in 2018.

Now answer this question: Who wrote 'The Kidnapping of Edgardo Mortara'?
David Kertzer