This is a freakly little book, one that I have read easily a dozen times. One of my dozen or so favorites.
Foster's THE MORPHODITE -- the plot -- is a loose, necessarily odd-structured assassination/fugitve story, and I have great affection for all the characters. BUT what captivates are the ideas.
The Morphodite character unites two crazy propositions, and two crazy propositions at the same time might be too many.
[SPOILERS? Pretty abstract, as spoilers go.]
1) A person is taught to change its own genetic structure and thereby change its body entirely, reverting into one of its own ancestors (or a new combination of its ancestral gene traits). In so doing, it swaps genders. That's a crazy proposition -- one that really affected my understanding of mortality, and which provoked me to read much more about genetic science.
2) In any social structure, there exist tiny variables that, altered or removed, may upset the entire structure. There are ways to determine the critical variable, change it, and overturn the whole applecart. And to observers at the time, the maneuver might seem invisible. That's a crazy proposition -- one that really affected my understanding of history and power, and which led me to study homeokinetics.
"It makes absolutely no difference whether we approach the universe from an initial position of truth or falsity. The truth will out, if we pursue it far enough, and the result will astound either origin equally." That's a quote burned into my head. It changed me, no kidding.
[END SPOILERS]
The book is followed by two sequels, TRANSFORMER and PRESERVER. The whole trilogy is pretty good, but it was Tiresio Rael in the first book who really got to me.