I've seen too often now where writers decide that their favorite world of their creation was not adequately explored in their original trilogy, so they decide to embark on second and third installments of their now-epic sagas. (Yes, Stephen Donaldson and Katherine Kurtz--I'm looking at you.) That's the kind of thing we find here.
Silverberg produced a respectable trilogy back in the day when he fired up with "Lord Valentine's Castle". (Technically, this is a science fiction series, but it can also be read just as well from a fantasy standpoint.) There, he introduced the world of Majipoor and its governmental structure of the Pontifex, Coronal, Lady of the Isles, and the King of Dreams, along with the myriad races that have come to call the planet home. It was pretty good stuff. I doubt many people would call Silverberg a master of characterization, but he's great at big ideas and setting up seemingly simple, almost archetypical, plots that take a few interesting twists and turns along the way. So with the original set of books, you got a solid and entertaining tale of one man's journey back to himself. Arguably, it's a minor classic of the genre.
Then, much later, Silverberg bumped out the curious and pointless "Mountains of Majipoor" as a fourth volume (with its slim page count and irrelevant arc, it's pretty much just Majipoor Helper), and not satisfied with that, evidently decided to go for broke and churned out a second trilogy, set in an earlier time. The first book of the new trilogy was interesting enough, the second was somewhat less so, and the creative juices have pretty much dried up by the third.
Not a lot remains to be said, but the author persists in saying it, and at times it feels like we're very slowly traveling across the vast surface of Majipoor with the heroes, slogging wearily along with every footstep they take. From the original series, we already know that we'll see the introduction of the Fourth Power, the King of Dreams, so all of the sturm und drang leading up to that seems like a lot of empty noise. Meanwhile, minor characters take up undue stage time for no substantial payoff later. And the villains are grotesquely villainous without any hope of redemption. Silverberg does take some time to delineate Mandralisca, but basically only to conclude "Boy, he sure likes evil."
Ultimately, the books plods to its climax and then drops in its tracks right at the very denouement. It's as if the author ran out of sheets of paper, or realized he'd hit his contractual page count. We're hoping for a big emotional and dramatic payoff, but instead we get "Everyone is hit by a two-ton truck. The End."
Very frustrating. Everything after "Chronicles of Majipoor" really is only recommended for the purists who want to fill out their collections. Otherwise, there's just not anything compelling about the later material.