Rabbi Shapira is especially well known because of a book he wrote while in the ghetto. The book, which is a compilation of weekly sermons to his students, contends with complex questions of faith in the face of the mounting suffering of the Jews in the ghetto. When it became apparent to Rabbi Shapira that the end of the ghetto and all its inhabitants was near, he transferred this book and other manuscripts to the Ringelblum "Oneg Shabbos" Archive. They were buried with other documents in a large milk canister which was found by a construction worker after the end of the war. The book, originally simply entitled "Torah Innovations from the years 5700-5702," was published in Israel in 1960 under the title "Esh Kodesh" ("Sacred Fire"). Daniel Reiser republished it in a two volume critical edition, "Sermons from the Years of Rage", in 2017.