Before I move into the brief analysis of why I despised this book, I would recommend anyone who felt strongly about the characters of the last book to keep away and possibly come up with their own ending. It will undoubtedly satisfy more, and prevent one's being disappointed with the execution of this novel.
From here, the spoilers.
One of my biggest problems with this book is the retrogressive development of her matriarchal and feminist themes. She begins the first book of the series by setting up two opposing worlds--one of violent patriarchy and another of peaceful but effective matriarchy--and then causing them to clash. What I thought was particularly effective, initially, was that the matriarchal society not only seemed to be the key to solving the problems created by the invading masculine forces, but it also seemed to bear the message that there was a way for the empowerment and coexistence of men and women. It was incredibly heteronormative, but it's a barely-disguised romance novel, so you don't expect much diversity. Regardless, I thought there were some incredible messages in the first book, which were also followed in later books.
The initial book seemed to say that women who supported each other and society at large would be celebrated, and women--such as Genvissa--who spurned sisterhood to rule in the world of men, reviled. And that never seems to quite disappear from any of the books. But the development of some incredibly horrible habits throughout the series reinforced a much nastier story under the surface. Every time a character does something horrible--such as rape--and subsequently shows remorse, they are forgiven. One of the characters develops from a pedophilic sadist into the main romantic protagonist in the space of a book, with nary more than, "I am attracted to this beautiful, good woman! Can I be good, too? Love redeems!" Personal slights, rivalries, power grabs: those are much harder to forgive, and causes ridiculous problems in later books, problems which could have easily been resolved by short conversations. So: personal conflict remains difficult for relationships, but actual murder and rape is grounds for future romance. Does it get any more fucked up? Characters in all four novels just shrug away violence, betrayal, and cruelty because it's done for the "Greater Good" but still get to maintain their status as Benevolent Gods/Beings. As a metaphor for the way leadership works, this has been carried off well by numerous contemporary writers, such as le Carré, and even G.R.R. Martin (although I won't hold him up as a literary hero). Nevertheless, it was one of the major problems with this book, because it seems as if the author herself wasn't able to contemplate the reality of the horrors visited on faceless victims.
There's also the concern--voiced by many before myself--that she spends three books developing strong characters and relationships, finally resulting in a couple long-term relationships with some hope of evading all the betrayal and drama of earlier books (when you ignore that the relationships largely exist between victims and their sociopathic torturers and murderers), only to throw them totally to the wind in the past book. I was strongly in support of her eventually making clear how much of a dick Brutus-in-whatever-incarnation is. Then to turn his three-time victim into an ineffective, traitorous tart is not only concerning, but terribly anticlimactic.
As the relationships between Noah and Weyland and Harry and Stella were either totally neglected or casually destroyed (without mention of its reparation or complete dissolution), I realized that--as with most cheap romance writers--Douglass is utterly incapable of developing a fictional relationship past its dramatic start or finish. Falling in love, betrayal, passion, sex--these are all very easy. They're dramatic, fun, eventful. Depicting stability, trust, even-keeled passion? For some, it seems absolutely impossible.
There are the further problems that, again, as others have mentioned, this book is devoid of movement. Most of the time is spent wringing hands. I think most of this could have been reworked into a novel half its size. Or, rather, had the author executed it well, a novel of the same size, with an equal amount of focus on the now-main protagonists as past important characters.
This book was supposed to take place in the London of the Blitz. You would barely know it. Save for the bombs that conveniently drop (no, truly, they're turned into plot conveniences) occasionally, there is little to no interaction outside of the major cast of characters. Everyone drinks a lot of whiskey and smokes a lot of cigarettes (absurdly so, actually) that it turns into a staged soap opera, without the real feeling of the era. I've read books by some truly terrible romance novelists who did a much better job of portraying WWII London, and it's incredibly disappointing. Instead of turning to advantage what could have been fun, it seemed to be an exercise in wrapping up the central plot and walking away, without any sense of atmosphere or having read an actual novel for enjoyment at all.
It was, in short, extremely poorly executed and disappointing. Relative to what Douglass did with her Tencendor series, I put forth that she was quite talented at writing novels, but lackluster when writing book series. For that, I am heartily sorry, as I was so excited about the first book in this series. My enthusiasm waned, and as you can see here, I am now heartily disappointed.