OK. I confess. I liked this series enough to order the last book from Amazon in the UK, just so I wouldn't have to wait for it. (I also saved myself a couple bucks because it was available in paperback there). That having been said, I found this book at times wonderful and at others god-awful, just like the other two books in the series.
If you haven't read the first two books, then you need to know that this series involves a one-armed genius who is a combination fightin' and rock climbin' machine and also the liberator of his world. The inhabitants of the world (Nulapeiron) live in an extensive series of caves that honeycomb the entire planet.
The first book covers the protagonist's rise from rags to riches (and back down to rags again) as he battles the ingrained caste system of his world. The second book covers the fight against an energy creature called "The Blight" which is gradually taking over the world. The last book involves the battle against the Blight's Daddy, the Anomaly.
One of the saving graces of this book is the story-within-the-story, which consists of a series of vignettes which take place about 200 years from our own time, and which cover the creation of a race of uber-mensch called The Pilots. The Pilots have the ability to throw lightning bolts from their eyes and can exist in the sub-basement of the universe called "Mu-Space". You spend all three books trying to figure out how this story is going to move the main plot-line along.
One of the reasons I bought this book is because Charlie Stross (whose fiction I adore) recommended it as great "hard Science Fiction". It is not. If that is what you are looking for, don't shop here. It is techno-gibberish through and through. If you want great hard Science Fiction, stick with Charlie.
This book is much more a science fantasy, a space opera, with futeristic deus ex machina geegaws. About the time that you start reading about people with the ability to warp space and time, and who use "femtatech" (one million times smaller than nano - COOL!) you know that you need to let out the clutch on your suspension of disbelief and let it ride.
What to say about this book? It's like Bill Baldwin's Helmsman series, but without the well-rounded characters and scientific grounding (that's sarcasm, if you're not familiar with the series). Hey, don't get me wrong - I LIKE space opera. I own ever Helmsman and "Sten" book made, and eagerly await more. However, good space opera this is not. If you want THAT, try Julian May's Many Colored Land series.
In summary - this book has lots of mediocrity interspersed with enough periods of brilliance to make you grind you teeth and cry out for a better editor. It IS a page turner, though. Wait for it to come out in paperback, read it with your bedroom door closed and don't admit you ever read it.