Well the obvious choice is the Path of the Dark Eldar series, which includes Path of the Renegade, Path of the Incubus, and Path of the Archon which comes out this month. Those are the only three actual Dark Eldar novels and are all by Andy Chambers.
Novels featuring the Dark Eldar though are a bit more common. Nightbringer by Graham McNeill, Iron Guard by Mark Clapham, Firedrake by Nick Kyme, Blood Gorgons by Henry Zou, the audio Deathwolf, and plenty of short stories scattered across BL's range.
LotN