I think that outside of the odd not-so-connected-to-the-ongoing-plot book and the recent e-book only releases centered around Quark, I might have read them all. Many I've read multiple times. The original post-finale works from Avatar through to Worlds of DS9 are just that amazing. In case anyone is interested, these are:
- Avatar (books 1&2) by S.D. Perry
- Section 31: Abyss, by David Weddle and Jeffrey Lang
- Gateways: Demons of Air and Darkness, by Keith R.A. DeCandido - and it's follow-up novella "Horn and Ivory" in Gateways: What Lay Beyond
- Mission Gamma: Twilight, by David R. George
- Mission Gamma: This Grey Spirit, by Heather Jarman
- Mission Gamma: Cathedral, by Andy Mangels & Michael A. Martin
- Mission Gamma: Lesser Evil, by Robert Simpson
- Rising Son, by S.D. Perry
- Unity, by S.D. Perry
- Worlds of DS9, book 1 (Cardassia by Una McCormack and Andor by Jarman)
- Worlds of DS9, book 2 (Trill by Mangels & Martin, Bajor by Noah J. Kim)
- Worlds of DS9, book 3 (Ferenginar by DeCandido and the Dominion by George)
The full list is much longer and continues on past this point - though that is likely best discussed (and also listed in detail) in the Trek Lit subforum.