I realize, belatedly, that I didn't talk much about the plot of the Demon Princes series in my last review; just as well, because that gives me something to talk about in my review of Jack Vance's The Killing Machine , the second book of that series.
I'm going to talk about plot in relatively loose terms, here, and this wouldn't be considered spoilish by anyone who reads the dust jacket copy, but still: some of this is stuff you don't find out until midway through the first book, so skip ahead to the next paragraph if you'd rather stay blissfully ignorant. Still here? Okay, then. The premise of the series is that the hero's home planet was destroyed by a conclave of the five Demon Princes when he was young, and he spent his entire boyhood and adolescence in training to take his revenge upon them. This means two things: 1) that the hero is a nearly omni-competent badass, and 2) that each book (there are five) is devoted to the attempted destruction of one of the Demon Princes. The villain of this book is Kokor Hekkus, the Killing Machine.
While the first book had a strong mystery element to it, this one is a more straightforward action-adventure novel. There are mysterious elements and plot twists and turns, to be sure, but the fundamental structure isn't that of a whodunnit. Still and all, it's similar in tone and quality to The Star King, so your reaction to that novel should be a solid predictor of your reaction to this one.