A trilogy is a single narrative spread over three books. This can be a very satisfying way to read a long, complicated story like The Lord of Rings. Continuity is key, however, and I can't imagine how hard it was to read those books as they were being published.
The Golden City, the last book in the Fourth Realm Trilogy by John Twelve Hawks, fell prey to this problem for me. The narrative picks up exactly where the second book, The Dark River, ends. Gabriel and Michael Corrigan, "Travelers" who can leave their bodies behind and travel among the six realms of existence, are taking separate and opposing paths. Gabriel is searching for his father among the realms, wondering what to say to his supporters, and, most urgently, planning to rescue Maya, his protector and lover. Gabriel's brother Michael is plotting to take over the Evergreen Foundation, public face of the Brethren or Tabula, who plan to control the world and its citizens using the Vast Machine -- the network of surveillance cameras and computers that track one's every move.
The book follows Gabriel and Michael through the fifth and sixth realms, unexplored in earlier books. It also follows Maya, who is having second thoughts about the rigors of her calling as a member of the Harlequin, protector of Travelers; citizen-turned-Harlequin Hollis; and evil-doer Nathan Boone as the Brethren moved to exert full control and the Resistance organizes to stop them.
It took me quite a while to regain the feeling for the story, with which I was quite taken when I read the first two books in quick succession. The urgency of the cliff hangers had left me, and I couldn't quite remember what the deal was with some of the minor characters. I had lost the story arc.
Consequently, The Golden City fell flat for me. The inventiveness and drive of the earlier books was not there. Instead, it felt like an ordinary finding-yourself kind of tale. There's the good brother who has to recognize his greatness, the bad brother who must be stopped, the turncoat bad guy driven by a tragedy, and a sinister cabal scheming to take over the world. It was all very predictable, and the Vast Machine seemed like an empty threat.
I can't say if I would have felt differently had a re-read The Traveler and The Dark River before reading The Golden City; I suspect I would have enjoyed it a bit more. I also suspect the stereotypical nature of the story, it's lack of nuance and character development, would also have shown up in the end.