Il va falloir attendre en effet, mais peut-être pas plus d'un an. Voici la réponse que j'ai reçue des possibles nouveaux auteurs :
Dear Mr.,
Sorry, at the moment the Leica IA book is not available, it is out of print. May be next year we will publish a new edition with some updates. But this time there will be only a German version. I will let you know when the book is printed.
Do you know our book 'Early Small-Format Projectors made by Leitz'? It is reviewed by Malcom Hart in: The Leica Society Magazine (UK), Number 18, June 2015, page 36. You also will find a review in German via the book shop site of the German Leica Society 'Leica Historica':
https://www.leica-historica.de/de/was-wir-tun/buecher.
Best regards,
Angela von Einem, Norbert Müller