As a suggestion it's probably best to read the three novels in the series back to back, or at least with minimal intermissions. The vast numbers of underdeveloped cut-and-paste characters tended to blend together after a while, and I spent a good proportion of this final novel trying to remember events in the previous instalment (read about a year previously) and who these individuals who appear with no introduction actually were.
Even more than before, The Naked God reads like a collection of a dozen or so sensibly-sized novels thrown up in the air and the chapters shuffled into random order. On the down side, that did leave me wishing that the author wouldn't keep switching away from a plotline as I was just getting into it, but on the other hand it did create an sense of anticipation and a desire to keep reading to find out what was going to happen next.
Anyway, having enjoyed the first two books I knew what to expect, but I soon discovered that it was starting to turn into a soap opera with each return to a familiar scenario giving me my momentary fix before hauling me off somewhere else without very much having occured. I also found myself becoming increasingly alarmed as the number of pages remaining started to shrink with no sign of an impending conclusion, or indeed any indication that the plot had any intention of wrapping up. So the fact that the ending was rushed was not a surprise - the fact that it was so implausible and unsatisfying undoubtedly was. As others have suggested, the author seemed to have tied himself in knots with no way to untangle the various strands of plot without using a big pair of scissors.
Anyway, despite the lingering disappointment, and despite the impression I may have given up to now, I did enjoy the majority of this book and definitely the series as a whole - I just wish the author hadn't let it slip so far out of his control.