Sequels are tough. There are expectations for sequels that don't exist for the first book, purely for lack of context. Sometimes, sequels are magical. Like, well, Harry Potter #2 through #7. Sequels like this work because they take the series up to the next level, go beyond expectations, grow along with their characters and readers. While Catching Fire (Hunger Games #2) felt very similar to The Hunger Games, it also complicated the series, raised the stakes.

Other sequels disappoint. For instance, Mockingjay (Hunger Games #3), which has a really messy, confusing plot that rushes across the finish. Or Allegiant (Divergent #3), which seeks to explain the premise of the whole series with obviously bad science—taking the series to a new level, yes, but not a good one. These books cave under the pressure of their predecessors.

I picked up Girl at the Bottom of the Sea (Chelsea #2) with high expectations because I had so much fun reading Mermaid in Chelsea Creek (Chelsea #1). In some places, the book delivers, but not all the way through. Mermaid in Chelsea Creek moves quickly from the real world we all recognize into a world of magic older than humans—both we as readers and the human characters—can really comprehend. Tea builds this world skillfully while also pushing the story along. I couldn't put it down.

But Girl at the Bottom of the Sea moves very slowly. The chapters alternate between Sophie's story—the story that Mermaid in Chelsea Creek began—and Syrena the mermaid's backstory. While Syrena's story is interesting, it slows the entire book down to a crawl. The backstory would have worked much better as a novella published alongside the trilogy or something similar. The way it's weaved into Sophie's story bogs everything down too much.

Sophie does make some progress on her journey, but very little. She hones her magic a bit and deepens her understanding of her quest, and moves from one point to another, but it doesn't feel like much really happens. Girl at the Bottom of the Sea opens exactly at the end of Mermaid in Chelsea Creek, in the middle of the action; no time has passed. Sophie and Syrena are leaving Chelsea to travel to Poland, where Sophie will begin training to defeat Kishka. Because the first book sets up the foundation of this quest, I assumed this book would cover Sophie's training, at the very least, and the third book would be the big, final battle.

In the first book, Sophie is informed that this quest will take her entire life. While I guess I don't expect the trilogy to cover her entire life—though why not, if the quest is that long?—I do expect it to cover a significant chunk of it. Yet, by the end of Girl at the Bottom of the Sea, we aren't that much farther into the quest than we were at the end of Mermaid in Chelsea Creek. This book ends just before they get to Poland. This leaves an awful lot for the third and final installment.