What worked: Think Jules Verne meets a latter day Alice in Wonderland. Eliza knows the dangers of the swamp close to her house. Still, she goes with her friends on a dare. When Eliza falls in a sinkhole, what she encounters is something right out of a Sci-Fi novel. There's humongous insects, spiders, and glowing people-like creatures. The author does a great job showing readers the wonder, horror, and terror Eliza witnesses. **Those huge spiders are right out of a Tolkien novel!
The other survivors take Eliza into their colony. Mary, is the 'odd' one of the group. She stays on Eliza to not forget her life on the surface and to fight to go back. Grayson is around Eliza's age and there is an instant connection between the two. There's also a little romance.
The biggest part is when Eliza does decide to leave the colony. A few rally around her, but others refuse to go. Apparently living under the ground makes survivors apathetic about leaving.
One problem I did have was with the idea of Eliza dealing with anxiety issues. It seemed as if she was able to bounce back too quickly after an attack. The darkness and just the idea of being far underground seemed as if it would make someone feel almost claustrophobic and panicky.
There's adventure, romance, fantasy elements, and a girl's overwhelming desire to go back to her family. Thrilling, adventurous underground ride. Add to that a protagonist who has to have the courage to face her biggest fears in order to find a way back home.