Hey Luth,
it's amazing how little it takes to recognise that face, right?
It's true, this book is available in every German bookstore and it had some attention in the press. I didn't follow that, though, and I haven't read the book - so I can't tell you much about it.
Hitler and humour? Well, did you know that the Jewish author Ephraim Kishon wrote a book named "Mein Kamm" about the topic? (The title means "My Comb" but sounds very much like "Mein Kampf", i.e. "My Fight", a book by Hitler where he describes his ideology.) But there is a strange kind of humour in Germany where you just have to allude to Hitler and people start laughing. "Hahaha - Hitler! How funny!" I've never understood this kind of humour and that's why I had no closer interest in this book. I'm curious whether you find it worth reading!
Cheers!
Markus