Middlesex by Jeffrey Eugenides
Enjoyable read, a little too tongue-in-cheek maybe for such a topic, but well researched.
Nothing shocking, or even revealing, if you know much about intersexual issues. The side issue (of incest) was the topic I found much more interesting.
Desdemona was a great, great character. Maybe one of my all-time favorites. It was worth the read just for her.