Youn Suu's first adventure ends up with her meeting Festina Ramos, and with her being infested with spores of the superintelligent but rather sinister Balrog, a hive mind. Festina, Youn Suu, her partner Tut, and two irritating Technocracy diplomats, then head off for the planet Muta. It seems that the Unity's recent attempt to colonize that planet has ended in disaster -- all of the colonists have disappeared, with only a brief SOS. It turns out that two previous groups of aliens on the planet also disappeared: the Greenstriders, and more ominously, the Fuentes. For the Fuentes are a group of aliens who mostly transcended and joined the League of Peoples thousands of years previously. Muta seems to be the only planet on which significant remnants of Fuentes technology survive. But both the Greenstrider and Unity colonization efforts failed despite ideal conditions...

The novel proceeds to a reasonably satisfying resolution of the mystery of Muta. Youn Suu's problem with her Balrog infestation is also pushed towards an interesting conclusion. Festina's story, that is the overarching story arc of the series, is advanced to some extent. The action of the novel is fairly interesting. There are even hints of alternate, perhaps more palatable, explanations of such things as the curious Technocracy policy about Explorers. And there are grace notes such as Gardner's description of the Unity, which to an extent read to me like an affectionate parody of Iain M. Banks's Culture (complete with special language). But... but... on balance I didn't like the book very much. Why?

Willing suspension of disbelief is a necessary feature for enjoying an SF or Fantasy novel -- or for that matter any novel. The reader must, for the scope of the novel, believe in what is happening. We must believe in the characters. We must believe in the technology, in the laws and customs of the societies portrayed. I've already hinted that I have a hard time believing in some of the basic ideas behind this series: the "Expendable" Explorers for one; and the League of Peoples' magical ability to determine (and enforce) their idea of "sentience". But I have mostly swallowed these to date. At times in Radiant my suspension snapped. Part of it was the invocation of concerns about "sentience"/"non-sentience": certain actions are deemed necessary to avoid League action. It seems that at times people (and governments) bend over backwards to avoid the slightest hint of negligence. Yet at other times, people and especially governments act with terrible lack of concern for the safety of others. I am forced to conclude that authorial convenience is the deciding factor as to when an action is "non-sentient". Another problem for me is the nature of some of the superhuman intelligences -- they are simply too powerful for my taste. A third issue is that I found the antagonists on Muta uninteresting. Finally, many of Gardner's previous books overcame my objections by being funny. One of the best ways to make a reader willingly suspend his disbelief in absurd things is to leaven with humour -- and this Gardner has often done in books like Ascending and Trapped. Radiant, by contrast, is almost never funny -- or, perhaps I should say, I found the characters who may have been intended to be funny (Tut and the two ambassadors) either cliché or simply wearying. So -- a weak entry in a series of books that I have found generally enjoyable.