A sci-fi adventure story about the adventures of a teenage boy named Jay, living on a planet called Erin (which has become isolated from the rest of humanity). Jay is obsessed with space and space travel, and finally gets a chance to live his dream.
Around the 1950s, Robert Heinlein wrote a long string of sci-fi adventure novels for young readers ("Have Space Suit, Will Travel", for instance) starring bright, eager teenage boys. This book feels like one of those; considering that Heinlein is one of two writers the book is dedicated to, I'd say that was intentional. I was a bit disappointed, actually, because I was previously familiar with Sheffield only from a few of his more sophisticated novels; this was not what I expected.
If this were one of those Heinlein books, though, it would be among the best of them; well-written and well-plotted. Most notably, the villain is one of the best-written villains I've ever encountered. He's not cartoonishly evil or cruel; he gets his way by intelligence and manipulation rather than force, but makes sure he has force available if it should become necessary; he doesn't make stupid mistakes; he thoroughly out-thinks the hero every step of the way. Even at the end of the book, when he's finally done something possibly stupid, it's unclear whether or not it worked out for him.
The worst aspect of the book was its treatment of female characters. Thanks to living on an alien planet where humans don't quite fit the ecosystem, and the available nutrition isn't quite right, male births on Erin outnumber female by about 30-to-1. Women are treated with both on-a-pedestal reverence; and condescension, not allowed to do anything remotely dangerous (such as go out into space). Midway through the book, after a teenage girl secretly gets on board the ship Jay is traveling on, one of his primary concerns for the rest of the book becomes protecting her and keeping the ship's sex-starved crew from knowing that she's there; because if they find out, they'll become uncontrollable slobbering Rape Monsters.
Why did Sheffield choose to make Erin's society like that? Presumably because he was trying to produce a genuine 1950s-style "boys' adventure" story, but figured that his 1990s readers wouldn't accept that genre's typical level of chauvinism without a solid reason. Fine. But it feels awfully dodgy, and not all readers will be willing to play along.
Aside from that, though: this book is fun, quick-moving, and smarter than you'd expect.