Speculative historical fiction is something I enjoy better than
   good science fiction ,probably because it involves Time Travel,
   which is _also_ my favorite Science Fiction topic.   Just the
   other day, I elaborated on "What if Edison's battery succeeded
   in winning that contract over Westinghouse?" at length and made
   a pretty persuasive argument that the energy crisis might not
   likely exist as it is today. [as battery technology wouldn't
   have stagnated as it did for so long, along with several other
   reasons]. Very satisfying.