All of the discussion about Cardassians in the philosophy got me wondering what everyone's favorite races are, and if you have a favorite book(s) focusing on them.
For me it's, in no particular order:
Klingons (A Time for War, a Time For Peace, Left Hand of Dstiny, Art of the Impossible)
Cardassians (A Stitch in Time, Terok Nor, DS9 Relaunch)
Romulans (Serpent Among the Ruins, ENT: Relaunch)
The Andorians are my second favorite Trek aliens (right behind the Vulcans).
They have the fierceness of the Klingons but because they're not as strong as the "Kingons" they have to use stealth and strategy to accomplish their goals. If you're going to have fullback aliens, you need to have a race thst's not quite as strong as Klingons. That is the role the Andorians play.