"Cobble Cavern" was probably a far more entertaining read than I could've expected coming into it. I haven't read a lot of cross middle-grade/young adult fantasy titles as of late, and this one charmed me - had me grinning from ear to ear as I read through and visualized the odd scenarios occurring. Olsen has a way of creating not only vivid depictions of magical mishaps, but he does so with whimsical execution. It features a wide cast of characters swallowed into an adventure filled with an array of mythical creatures and harrowing situations that it kept me engaged for much of the novel. The story revolves around Flin, a boy traveling with his classmates, teachers and chaperons from New York to Ireland for a debate competition. But the trip gets severely derailed after a sudden earthquake sends their spiraling down into the depths of the Earth. As the group struggles to find their way back to the surface, they have to contend with many creatures of the unique underground caverns, including the novel's namesake. Flin comes to terms with some unique abilities, and follows in his grandfather's footsteps as he journeys an embraces his destiny. There are a lot of characters to keep track of in a short time within Cobble Cavern, but each of the characters has their own unique charms and attributes to keep them distinct. By far, I thought Flin and Pilt had the most impact on me, not just for their friendship, but their dynamic interactions. Flin's a brave boy and not afraid to push himself to do what needs to be done - and I like proactive protagonists like him. It's interesting to see how involved both the kids and adults in the novel are, and to get a sense of their motivations and awe while on this incredible journey. I understand that this is book one in an ongoing series, and I'm more than intrigued enough to check out the sequels, not just for the characters, but also to see more of the world that Olsen creates. Overall score: 4/5 Note: I received this as an ARC from NetGalley, from the publisher Cedar Fort.