From what I understand, the Tzenkethi war book was just an idea tossed around, not a solid story, a couple of editors ago as one of the projects he was really attached to, but he was then let go from the company, and the idea pretty much died with him.
As for the Stargazer novels, although they can work as standalones, they really work best together, as there's an ongoing narrative. They they take place close enough together to basically serve more like a six or seven (if you want to count The Valiant as a Stargazer novel) part mini-series, as opposed to an ongoing series. I remember certain ongoing plots favorably, but individually, I don't think they really did a whole lot with the setting that couldn't have been done elsewhere. I think for me, each book had an A-plot and a B-plot, as well as touching on the ongoing plots, and either one or the other of the main plots didn't quite work right for me.
I think, though, that the series is short enough that you could easily try the whole thing out - they're short reads, with I think only The Valiant actually hitting over three hundred pages.
