Middlesex by Jeffrey Eugenides
It's about a European brother and sister that leave during WWI and migrate to Michigan... and get married. They have children, one of which marries their cousin. One of the cousins' children is born a hermaphrodite (through a rare genetic disorder they both share in remission, being family and all) who was mistakenly mislabeled as a girl and raised as one for the first 15 or so years before "switching" sexes. I won't say any more than that because the book is absolutely fascinating and you have doubts whether it's fiction at times because it feels so real.
9/10 - The first half of the novel is the most interesting as it follows the travels of the brother and sister as they fall in love and get married. I couldn't put the book down.
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