Emilie and the Hollow World -- Martha Wells

Emilie and the Hollow World is Martha Wells' first book specifically for a YA audience, though I think her Raksura novels would fit right into any YA collection.

Let me say right off the bat that I'm a sucker for hollow world stories.  Put me in Pellucidar or send me off on a journey to the center of the Earth, and I'm a happy guy.  So naturally I was predisposed to like this book.  It doesn't disappoint.

The story takes place on an Earth-like world in a steam-punky time in which sorcerers can work with the aetheric current and find pathways to the underground world, which can be reached through the sea or through an opening like a volcano.  The first man to make such a journey has disappeared, and his daughter, Lady Marlende, has mounted an expedition to go and look for him.

Emilie is a runaway, and with good reasons, which we discover as the story moves along.  She wants to go to live with her cousin and go to school.  To get there, she has to stowaway on a ship.  Her plans are upset by some mysterious doings on the docks, and she winds up on the Sovereign, the ship that's about to descend below the ocean.  By the time she's discovered, the trip is underway and the adventures have begun.

Wells is excellent, as always, at world-building, and the societies that Emilie and the others encounter are interesting and believable.  There's plenty of intrigue, danger, and action, too, and Emilie proves herself more than capable of dealing with just about any emergency.  If you read YA fiction, this one is great fun and should be on your list.