This Halloween, bypass the usual vampires and werewolves of teen fiction for what lurks between the covers of Francesca Lia Block’s brutal, beautifully written “Love in the Time of Global Warming.” Those fanged and furry creatures are but a sugar rush compared with Block’s genetically engineered giants as she treats us to a dystopian tale tricked out in her signature lush prose. In the opening pages, Penelope sees her loving family and the fantastical city of Los Angeles disappear in the flood and fires that follow a tremendous earthquake. One of few survivors, she steals the van of the marauders looting her home and sets off into the ruined landscape. Block loosely styles Penelope’s journey on “The Odyssey,” with Homeric figures intriguingly updated, including surgically enhanced sirens in the “swamplands of Beverly Hills” and Circe as a cake-besotted soap opera star. Penelope is no buff, bold hero but a grieving, relatable girl “stuffed full of fear.” She believes that her younger brother may be trapped in a giants’ lair, and as she travels there, she joins forces with several shaken, gay teens. The heart-wrenching showdown occurs in Las Vegas, where the wreckage of a faux pyramid and Eiffel Tower hints at global destruction. As Penelope connects with a new love and strives to protect her friends, Block asks readers to rethink the role of hero. Penelope grows to become not just a skilled sword-wielder, but also a talented weaver of stories that warn, chronicle and save.