Invasion! is compatible. (There's a reference to the Furies in SCE: "Ring Around the Sky", and one of the characters from Time's Enemy appeared recently... I believe in the first DTI book.)
Millennium is mostly compatible - I'm not sure the epilogue is anymore.
One of the SCE ebooks references the Invasion series, so it is part of the current Lit-verse.
First, the Furies built the Kharzh'ullan space elevators, which the Tellarite colonists then refurbished and used in the 24th-century.
If I remember correctly, my thinking was this -- in a universe of cheap energy and easy matter transportation (which describes the Star Trek
universe pretty well), space elevators don't make a lot of sense because they're much more expensive (in terms of energy and materials) than transporters would be. So the elevators needed to be built by someone who specialized in brute force engineering. That, to me, said the Furies because what we saw in Invasion!
indicated a people whose development skipped the easy and elegant tech we see in the 23rd- and 24th-centuries. Also, the Furies weren't really a bad people; they happened to be on the losing side of history in lot of ways through no fault of their own (which is why I don't like what Janeway does to them in The Final Fury
), but they built a starspanning civilization and they should have left interesting (and useful) relics behind. So I wanted to show a different side to their legacy.
Second, I put Tev on one of the other Starfleet ships in Soldiers of Fear
. In retrospect, I probably wouldn't do this now if I were writing Ring
today; I didn't do anything with it, and it didn't go anywhere. That said, some of the other SCE
authors told me they thought that was a neat touch.