Wow! This is extremely good hard SF. There is a quote on the cover from Charles Sheffield stating that 'If You Wonder What Happened To The Science In SF, Read This Book'. That is definitely true

A spaceship accidentally crosses into an alternate universe, one where the force of gravoty is one billion times stronger than ours. Strong enough that people have detectable gravity fields. They survive! Five hundred years later their decendants are faced with another problem. The nebula in which they are living is becoming uninhabitable, and they have no way of stopping it.

This book is wonderfully written, and the scientific content superb. This is most certainly not your typical space opera novel. Baxter explores the society that has developed (or atrophied) during the five hundred years in this alternate universe in a precise detailed manner without seeming at all verbose. The characterisation is thoroughly believable, the people in the book engaging and fully rounded. I read this book as a direct result of having read Baxter's collaboration with Arthur C. Clarke early in the year and wish I had started one of his books years ago. The good news now though is that I have many of them lying in my reading future