I recently purchased a newly published book about Max Berek. Unfortunately, so far it is only available in German. The book was published by Dr. Knut Kühn-Leitz with the titel
Schöpfer der ersten Leica Objektive
Pionier der Mikroskopie
It is a fascinating read, especially because it parallels many phases of the development of the Leica.
I am currently trying to obtain permission to use translated passages of the book for publication on this blog.
The book is published by: Lindemanns Verlag