Maurice Willson Disher's review in The Times Literary Supplement of 29 November 1941 began, "To believe that N or M? is not Miss Agatha Christie's best is difficult while the first fine anxious rapture of her latest story is still troubling the mind." He concluded, "The point is reached when you begin to fear for your own sanity on catching yourself wondering whether an ingratiating babe-in-arms might not be Herr Doktor in disguise. Yet such is Miss Christie's skill in conjuring up the ominous that even infant prattle sounds uncommonly like a code for the Fifth Column. In other words, as Mr Robey has said before now, N or M? gets you."The Times Literary Supplement, 29 November 1941 (p. 589)
