You remembered right! His real name was Kurt Erich Suckert and Malparte was a play on Bonaparte. He was a friend and was also imprisoned (island exile - how Roman!) of/by Mussolini. One of the very strange scenes (there are so many) was summer salmon fishing with Himmler above the Arctic circle in Finland.
I should also add he wrote about the American occupation of Naples in The Skin. Not quite as compelling a book but of interest certainly.