Okay, so I finished Servant of the Empire by Raymond E. Feist and Janny Wurts last night. Here's my thoughts.
I'm not a huge fan of the romantic subplot between Mara and Kevin. A lot of this is just because I'm usually not a fan of them in general (a point most people are probably sick of hearing about by this point), but in this case it goes deeper than that.
I will grant that this one is better than what you'd ordinarily find in a Feist novel. I think that's probably Janny Wurts' influence, but again, as I haven't read anything she's written that she didn't cowrite with Feist, I can't prove that. Both Mara and Kevin have their own arcs that exist independently of their romantic subplot, and they have their own motivations. It also doesn't get a happy ending.
However, I'm not entirely convinced that Servant of the Empire really earned its romantic subplot. While it is better written than most Feist romantic subplots--and, if I'm being honest, most romantic subplots by any other author I've read--there's a couple of points that mean it had to go a lot further than it did.
One is that Kevin is a slave. The Tsurani form of slavery is built in such a way that there's no way for a slave to ever be freed, outside of a couple of very specific situations that are difficult to replicate. This means that it's both harsher than a lot of historical, real-world forms of slavery (as abhorrent as slavery is, at least real-world slaves can occasionally either escape or be released), and harsher than the form of slavery common in Kevin's homeland, the Kingdom of the Isles (where it's only applied as a punishment associated with life imprisonment).
Because of that, this is never going to be a relationship between equals. To Servant's credit, this is a huge part of Mara's angst over the relationship, and it does feed into several plot points along the way.
My contention is that the book is adamant in acting as if this was a consensual relationship, or at least would be if it weren't for the slavery issue. That's not really the angle it should have come from. If the Mara-Kevin romance was going to be a thing no matter what, I think the emphasis should have been on how Kevin not only didn't consent to it, he never would. I think this would have made a lot more sense given the power dynamics and given that Kevin was previously a Kingdom noble who'd been fighting against the Tsurani invasion.
I don't think it'd make sense for him to just live with it because to him, this form of slavery should be so offensive that he sees it as a moral imperative to resist anything Mara wants. Kevin is introduced as a slave that incites trouble with the other slaves anyway, so this would make sense given how he's introduced.
My other contention is that I don't think this is necessarily the most interesting path they could have taken Mara down. I think it would have been a lot more interesting if, after having ascending to power by accident (after almost taking religious vows at a Tsurani equivalent of a convent), and after experiencing Bunto as a horrible husband, her response had basically been to swear off relationships altogether.
This too had been a small part of her arc anyway. While she was aware that there was a cultural and political expectation that she'd eventually remarry another member of a noble family, she wasn't really entirely sold on the idea. The story tries to chalk it up to Bunto being a bad husband and her blooming romance with Kevin, but I think it would have been more interesting if the actual reason had been that she just didn't find sex or romance particularly appealing.
I think this would have been a better fit for her character arc in general, too. A lot of Mara's decisions over the course of this book (and the previous book, Daughter of the Empire) is based around her being unconventional by Tsurani standards. So why not have it so that even independent of Bunto's treatment, she already leaned towards being aromantic or asexual and probably wouldn't have sought out a romantic pairing if it hadn't have been for the family she was born into?
Even if they went down this road, they still could have kept owning slaves as one of Mara's character flaws. It's mentioned at one point that she hadn't really thought of how difficult having Bunto around had been for her servants until years after the fact, so it would have made sense that she'd never consider the moral issue of slavery up until, say, Milamber's departure from Kelewan. It's an established part of her character that she isn't always the most empathetic person when it comes to people she either doesn't know personally or regards as being beneath her station. (And, in fact, by extension, Tsurani society rewards this trait to an extent because the entire society would crumble if people in power had higher degrees of empathy.)
It's especially unfortunate because other than this subplot, Servant of the Empire is actually pretty decent. It manages to avoid middle book syndrome--the plot continues moving in this book, so it's not all just setting stuff up for the third book. This is probably for the best because, depending on what edition of this you get, the book is over 800 pages long.
It also manages to continue avoiding the big problem with interquels--that is, it isn't just relitigating the same plot points from a different perspective. There's a few points where stuff that happened in Magician and Silverthorn are brought up and they do have an impact on this book's storyline, but they're not the main focus. The story remains about Mara and her political maneuvering, not on the fallout of things Pug/Milamber did in the main series.
So for the most part, I do think it's worth reading; I just think it gets derailed a little bit because of a mishandled romance subplot that didn't really need to be there.