I have to admit I haven't read many EU novels or comic books, so my knowledge of the Expanded Universe comes mostly from Wookieepedia. I have read many more New Canon novels, and I really like their development. I think my Top 3 favourites are, in no particular order:
- The Levers of Power: Rae Sloane commanding a Star Destroyer during the Battle of Endor.
- Lost Stars: Two friends grow up during the time of the Original Trilogy and until the Battle of Jakku and get involved in galactic events.
- Bloodline: As tensions rise in the New Republic, Princess Leia discovers a plot to undermine the NR. This happens 6 years before The Force Awakens.