Andrei, would that be possible to give us access to the .css that gives
the mobi file its global appearance? I'd like D-related mobi/epub that I
create to have the same look-and-feel.

https://github.com/D-Programming-Language/d-programming-language.org/blob/master/ebook.css

https://github.com/D-Programming-Language/d-programming-language.org/blob/master/ebook.ddoc

See also the makefile.