Re: Novels set in the Trek universe... but not about Star Trek?
I'd also throw The Art of The Impossible in there. It's kind of a political thriller about The Betreka Nebula Incident that Garak and Bashir discussed in The Way of The Warrior. It covers 18 years, and features a bunch of different characters, some of we never saw on screen. There are a few recurring characters from the TV series, and a couple of major players from the novels, but I don't think there is a single main character from any of the TV series.
They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance. - Terry Pratchett, Equal Rites