I think this is another of those books where if I had read it at a different age, I would have loved it.
This is the story of Sham, a boy whose guardians place him as a cabin boy on a roving train. He slowly learns the ins and outs of life aboard the moler train and the railsea (analogous to our whaling ships and oceans, right down to the fantastical creatures lurking in the depths). On one of the wrecked trains they pass, he finds something that seems impossible, and that's what drives the rest of the story. Along the way, he meets up with pirates, explorers, hunters, subterrainers, friends, kidnappers, liars, and thieves.
One part Moby-Dick, one part Huck Finn, and half a jigger of Robert Louis Stevenson, with a pinch of Narnia and set on a dry(?) planet in a galaxy far, far away, Railsea has some major pluses:
--Exquisite and playful language
--No unrealistic precocious romance
--Strong female characters
In also has one major drawback: I just wasn't racing to read it. It took me more than a week to finish, when it should have taken a few days. I liked Sham, the trainfolk, the setting, etc., I just had trouble getting lost in the story. But I think if I had gotten hold of this one when I was, say, 11 or 12, I would have given it 5 stars.
I will also add that I'll never look at antlion hills the same way ever again. :-)