Fiction: this book is a fabrication of the author, who appently met Adolf Hitler only 3 or four times and never alone. It first appeared in 1939 and was translated into German in 1940. It was a best seller and has had many follow-up editons (WorldCat lists 264), lastest being in 2015 (Danish) and in 2012 (original French and German).
Articles and books have been written about its authenticity. The best summary is given in a German Wikipedia article "Gespräche mit Hitler" [ https://de.wikipedia.org/wiki/Gespr%C3%A4che_mit_Hitler ] which surprisingly has NOT been translated or re-written in any other languages.

Hitler m'a dit, une source discréditée

L'authenticité des propos attribués à Hitler par Hermann Rauschning dans Hitler m'a dit n'est plus que rarement admise. L'historien britannique Ian Kershaw juge notamment : « Je n'ai pas une seule fois cité le Hitler m'a dit de Hermann Rauschning, ouvrage dont l'authenticité apparaît désormais si mince que mieux vaut carrément l'oublier ». Après Theodor Schieder, Wolfgang Hänel, Fritz Tobias et Eckhard Jesse ont mis en évidence le peu de crédibilité de l'intimité avec Hitler revendiquée par Rauschning. Celui-ci n'aurait en fait rencontré Hitler que quatre fois, jamais seul à seul, n'aurait donc pu recueillir de telles confidences notamment politiques, et aurait puisé son inspiration essentiellement dans la littérature de l'époque. Son témoignage est en particulier jugé invraisemblable à propos de supposées convictions cachées de Hitler à l'encontre de la religion chrétienne, dont il est le seul à faire état.

En 1985, l'historien Wolkgang Koch, citant approbativement les conclusions de Henry Ashby Turner selon lesquelles on doit accorder peu de confiance au livre I Paid Hitler, publié sous le nom de Fritz Thyssen mais écrit par Emery Reves, ajoute que le même Emery Reves aida Hermann Rauschning à écrire le livre Hitler m'a dit.

Source : http://fr.wikipedia.org/wiki/Hermann_Rauschning

Also known as "Hitler Speaks". This is an incredible book to read. Hermann Rauschning was President of the Danzig Senate and had actually met Hitler a few times which have been historically proven and noted in his other book "The Revolution of Nihilism" which he says he had met with him 3 or 4 times. This book on the other hand makes it appear that he had many more meetings with Hitler than he previously stated. It has been shown by historians that much of what is stated in this book has been taken from many sources, speeches ect., and were not taken from personal conversations with Hitler. In fact he in all his meetings (3 or 4) he was never even alone with him. Bluntly put this book is basically Allied propaganda although damn interesting propaganda. I honestly believe many of the stories of Hitlers psychosis and involvement with magic may have actually had their start from the last chapters of the book. Read with a grain of salt, heck with the whole salt shaker, but read it nonetheless. ( )