Even though the theme is a bit heavy (hello, death and prolonged grief), Missing May is written for a young audience. The writing is simple and straightforward, and Summer provides a relatable character for young adult audiences to truly understand the concept of grief and mourning. Through Summer, we get to see what it's like to deal with death from the perspective of a twelve-year-old who's also dealing with normal junior high stuff.
This is a book that is definitely about family—no matter how messy or imperfect. Summer's family isn't exactly a "normal" one, but it's one that works and one that's filled with love. The book deals with the idea that family is of your own choosing and making, and even though Summer may not be their biological child, Aunt May and Uncle Ob still love her to bits and pieces. And even though Aunt May dies and leaves Uncle Ob and Summer flailing around in confusion, they still manage to piece together their own version of a working family.
Maybe a three-hour drive doesn't sound like the most exciting quest to you (you don't even really need a gas station break with that kind of trip), but it's a big deal for Summer, Uncle Ob, and Cletus. They're literally heading out on a quest to bring back the dead, which makes it seem more like something that a Greek god would do. And their little trip to Putnam County and Charleston does bring them to their goal in the end—they process their grief, manage to feel closer to May, and get to see life in a shiny new light. We'd call that a successful day trip.