While "Chaos and Order" isn't as tightly plotted and intricate as "A Dark and Hungry God Arises", it is still rippingly good. The tale is a rollercoaster from following-on beginning to incomplete end, unlike the previous book, which more amounted to an examination of shifting alliances and intrigue amid the profound psychology of its characters, all concentrating and shifting onto one place, accruing to a kind of psychological "critical mass", at which point Thanatos Minor explodes. One of the core themes of Chaos and Order - running about through a maelstrom of rock, the hurtling debris of shattered plans, shattering and coalescing into new forms - follows on from the diametrically opposing theme of the previous story brilliantly.
As the web of intrigue and murder in and around Earth is expanded to a fully-fledged political thriller, we have the important characters from the previous story - Nick, Morn, Angus, Davies, Vector, Mikka, and with them the rather incidental Sib and Pup - all saved from the storm of Thanatos Minor's ruin and flung off just ahead of half a dozen people who want them alive; or, if they can't have them alive, then blown to atoms like Billingate. Everyone else - from *Captain's Fancy* - is dead. While this may seem like a bit of a *deus ex machina* (subtle nod towards Angus, I'm sure), in practice it works out fine.
They are now on the run, the most explosive body of information in Human Space, and seeking to make themselves even more explosive by letting Vector Shaheed, the geneticist, complete the anti-mutagen drug which the United Mining Companies Police suppressed, which will give humankind a defence against alien absorption, however temporary. Everyone - the cops, the aliens, people working for the cops and people working for the aliens - are after them, and the scene is set for ever-tenuous alliances and furious desperation to lead to a lot of shooting and bloodshed, and even greater extremity by the survivors.
This is an intermediate tale. As with all the others except "The Real Story", it is successfully diametric and harmonious in its many balancing qualities. It is a masterpiece, in a way opposite to how the previous book in the story is - and again this is an intentional contrast. I swear again, this series will significantly improve your life. I'm normally so damn analytical, and it has me ranting!
The marking of four out of five and not five is rather a personal opinion. I preferred the rigid and less scattered nature of the plot in and around Billingate, and this made me like the fourth book somewhat less than the third. The horror of the first, second and somewhat the third books as gone, or at least vastly reduced and changed in character. It is no longer an issue. The squeamish will have been well and truly left behind by now, anyway.
Each book in the Gap Series up to this one expands on the author's complex mind-game universe by a power of two. It is this story which opens Donaldson's future to its fullest extent. The final book is an examination of that universe, now that the previous four books have detailed it in full and lavish detail, bringing the story to an ultimate conclusion. This fourth book is the last time you will see the fun "Ancillary Documentation" - but Donalson's story-advancing characters will have captivated you utterly by now, if you've got this far, so you won't mind that in the slightest as you rapidly and nervously go out for the fifth book, hand shaking as you hand the money over and wonder whether it can possibly live up to what's gone before.