For those interested. I found the book I read. https://books.google.de/books/about/Der_Computerdieb.html?id=eJHFSgAACAAJ&redir_esc=y
It is german, and I think there is no english translation.
It has a paragraph with some basic code. This lines where the first code I ever typed into a computer. It is not really a game more a screensaver. But it is enough to impress the 10 years old me.
+1 for this. Jazz Jackrabbit is my all time favorite DOS game. I remember, me and my sisters playing this all day and night back around 2000. Some weeks ago i retried it. Was really fun ?