Good news first: Heaven's Fall is the final book in the Heaven's Shadow trilogy. At the end of Heaven's War, the alien space ship (or rock) Keanu has in fact turned around from its path to leave the solar system and the 200 or so abducted people from earth are on their way home. Or so it seems. The return trip has in fact taken the best part of twenty years because the rock is somewhat below is usual functionality. In keeping with the spirit of the previous two books, the characters still have their "we might as well get used to it earlier rather than later" attitude. So instead of trying to send everyone back to earth, they only rebuild a small lander for six people who shall save the earth from whatever has befallen it (remember, those bad Reivers dropped off earlier). Also, they have started to seriously produce offspring (one fourteen year-old they - of course - bring along on the trip down to earth).
Luckily the Reivers have taken a laid-back approach at taking over the galaxy and only occupied parts of the Western world, where they are trying to build something very dangerous. In the meantime the Keanu team crash lands in India, where people are completely indifferent about the alien invasion. We might as well just accept it, I guess... if it weren't for that something that is being built in the Free Nation US and the handful of Keanu visitors who then try to get to it and stop it. Naturally they are caught, but left alive (for whatever reasons). Naturally also, the Reivers assign a human to push the final button because they themselves can't make decisions that would not only threaten the Architects home world but also endanger all life on earth. Ouch! But at least this is consistent within the trilogy; the whole crisis is completely bootstrapped and nothing is achieved. The Architects could have just steered their space ship into the sun and all would have been well. Everything that happens is directed by the Architects, but they never do it themselves. Ouch! Ouch!
The more I think about it, the more satirical it appears. Unfortunately the editor had lost interest earlier; the typos and grammatical errors start piling up towards the end of the total 1200 page exercise. The storytelling is becoming a chore when information is available from point-of-views that should know nothing about it. The authors' previous trick was to use the Revenants' supernatural connection with the Keanu object to relay this information. In the end it just becomes sloppy. The same way in which some of the aliens' point-of-view is used to build reasoning behind the protagonists do-or-die decisions that otherwise wouldn't make any sense. It may be appropriate to use the characters' speech in screenwriting to point things out directly, but in a novel I don't consider that a good interpretation of the rule "show it, don't say it." Even (or especially) if the information is completely irrelevant.
Fun fact: the dangerous thing that is being built in Arizona has a diameter of 10 km which (as one of the characters rightly states) is larger than the LHC (by about 15%). Comparing this to the SSC, would probably require too much research in wikipedia. But it naturally raises the question why it is built above ground... or maybe it is the other way around: why is LHC is so deep underground?
I'm staying with my three-star rating as before. I'm just too indifferent about the books to not like them.