Since the Marvel comics, newspaper strips, and Thrawn books have already been covered:
COMICS
- The Boba Fett comics (all the ones published before 2006)
- Crimson Empire (there’s also a Crimson Empire II & III, but the second’s not as good as the first and the third’s a prequelized waste of time)
- The Jabba Tape
- River of Chaos
- Tales of the Jedi
NOVELS
I recall also liking The Truce at Bakura and the first two Lando books, but it’s been a couple years since I read them. I’ve also read the first book in The Han Solo Trilogy by A. C. Crispin, found it a great novel, but haven’t yet read the second two books in the trilogy.