Critics overwhelmingly praise Klemperer's I Will Bear Witness: A Diary of the Nazi Years, 1933-1941 for its accessible style, its compelling story, and its historical significance. Peter Gay of New York Times Book Review comments, "To read Klemperer's almost day-to-day account is a hypnotic experience; the whole, hard to put down, is a true murder mystery—from the perspective of the victim."

Because Klemperer never intended his diary for publication, critics find that it rings true. Omer Bartov of the New Republic observes, "Klemperer's diary has the immediacy and the poignancy of unedited notes written in the thick of experience."

That Klemperer dreamed of writing his memoirs but feared they would never be completed is ironic given the global audience his diary has reached. The character of Klemperer himself is, in fact, part of the book's appeal. Critics commend him for his humanity, integrity, courage, and...