This book is tight. Baxter begins with a simple idea: What would a universe be like if the gravitational constant was 1 billion times greater than in our universe? The largest stars would only be 10 miles across with life spans of less than a year and no planets. Individual humans would have gravity fields, and nebula of breathable air would encircle black holes that sucked in the stars as they died (and everything else). Baxter then adds a small community of humans to this universe. 500 years in the past a ship crossed the barrier between the two universes, and while the ship was destroyed, its crew lived. Their descendants live in a rigid caste system (complete with untouchables) in a nebula that is dying.

The set-up is the mundane stuff of b-list sci-fi: the humans are dependent on old technology they no longer understand, a young man comes of age and shakes everything up (whilst also touring the world in which the book is set), some people resist the new ideas the young man comes up with, and various political and personal conflicts ensue. However, Baxter's treatment of this situation is anything but mundane. His handling of the political difficulties are particularly well-done, in a painfully honest way. The people who inhabit this universe, although removed from us in time and space, have all the same frailties that plague our current world -- with one notable exception.

The pacing is excellent, although there is at least one side trip that I could have done without. I have only two criticisms of the book. First, the young hero is a superman -- intelligent, strong, resilient, resourceful -- he has none of the flaws that so mar the other characters in the book. It's really too bad. Baxter missed the chance to create a really compelling character. Second, the descriptions are sometimes difficult to translate into a mental picture. I had a hard time imagining what some of the central locations looked like, even after carefully rereading the descriptive passages.

The ending is fabulous. Baxter ties all the plot points up while remaining true to the characters he has created -- there are no shifting motivations or sudden changes of heart. Baxter's hard-edged political realism is carried all the way through the end. Although I typically ignore cover blurbs (have you ever seen a negative one?), this book has the best blurb I have ever seen: "He writes like I used to ... I should have him assassinated before it's too late" (Larry Niven).

Note: This book is based on a short story by Baxter of the same name. It The characters in the story have the same names and personalities as characters in the book, but they have very different biographies. The broad outline of the short story is the same as the novel, so beware of spoilers.