This is the continuation of the story begun in 
Pandora's
 Star. No, I don't mean the sequel; "Pandora's Star" was only
 the first half of an almost 2000 page novel (I wonder why they didn't
 publish it in one volume?).  It picks up where we were left: halfway
 through an interstellar war, terrorists fighting against alien
 subversion, one of the protagonists disappearing over a waterfall.. This
 book picks up all those threads and more, and weaves them into a
 coherent and satisfying whole.
 
 It's difficult to talk about 
Judas Unchained alone, so what
 follows sometimes refers to the novel as a whole. Bad points first: some
 of the characters keep just happening to come across one another on
 different planets. The climax is a little contrived, with an over-long
 chase and a series of will-they/won't-they last minute situations. And
 the story would have been better if one of the lengthier threads, about
 the Silfen Paths, had been 
much shorter.
 
 I've mentioned the novel's length. It seems to be a law of nature that
 the first 20% of any book must be spent introducing the characters, the
 situation and the plot; and this is inevitably less exciting than the
 other 80%. 20% of 2000 pages is a lot! That part of 
Pandora's
 Star reads almost as a series of separate stories, most of which
 seem to be mere background material. Fortunately Hamilton has a good
 enough writing style that I didn't find this too much of a problem; not
 even the political intrigues which are usually synonymous with 'dull'.
 Now in 
Judas Unchained all these threads, and almost all the
 characters, are dexterously woven into the main plot. This is what
 impressed me most about the novel: despite its length, complexity and
 scope, Hamilton not only fits everything together, but makes it seem
 effortless.
 
 Characterisation is adequate, though not the book's major strength. The
 plot is good, but the world-building is first class. The consequences of
 such things as easy-but-expensive rejuvenation and of memory storage are
 explored; for example, murder is punished with a real suspended
 sentence. Travel between inhabited worlds in different star systems is
 by means of wormholes, but in a stroke of genius Hamilton creates a
 railway system, with the trains carrying passengers through one or more
 wormholes to a station on their destination planet. And it's a sign of
 the richness of the world-building that, despite the size of the book,
 there are facets that are underplayed: a sentient AI, various other
 alien species, genetically modified humans...
 
 Who should read this book (and 
Pandora's Star of course)? Anyone
 who likes hard-ish SF and is willing to spend the time it takes to get
 through 2000 well-written pages. If you do, the world-building and the
 choreography of the story-lines will be your reward.