What is a claim about gender identity made in the book Love in the Time of Global Warming by Francesca Lia Block?

Francesca Lia Block's young adult novel Love in the Time of Global Warming reforms Homer's Odyssey into the dystopian story of a modern seventeen-year-old girl named Pen (in the original epic, Odysseus's wife is named Penelope).  The book has a lovely feminist lens to it, with Pen being the one to go on her own journey, rather than waiting for a man to come back from his, as the Odyssey's Penelope had to. 
The book embraces conversations about gender identity and sexuality. Pen is bisexual, Hex is a transgender man, and Ezra and Ash are both gay. While I would personally say that Block has a bit of work to do in terms of writing about trans characters, the book's overall message about gender identity and sexuality is very accepting of people who transition, saying that the identities of the characters in the book are valid ones.