I have read the manga and bought all of the books. A very beautiful story showing how gender can affect the way you act and feel, but not who you are. I only truly understand after finishing the two extra books what the author really wanted to tell us. My view of gender and sex has developed into looking at people ignoring their appearance and biological gender but interacting with them as solely humans. Gender doesn't define a person, it only highlights aspects the person already has or helps making those visible. Genderless people, like the main character in the gender of mona lisa, radiate a form of peace I can't quite understand but are pretty interested in.
If you find yourself interested in this topic, you might enjoy reading this story
Seibetsu "Mona Lisa" no Kimi e.