My favorite(s) are The Han Solo Adventures by Brian Daley. They're well written, very interesting, have that depth of character & atmosphere, that attention to scene detail that Daley was so good at - and - they're free of the burden of all the stuff that is just so fucking tired to me about Star Wars, i.e. The Empire, The Sith, Vader, R2, 3PO, etc. There is just so much more that can be done with the vast, dark, unknown universe we were introduced to in 1977. Brian Daley did it with these three novels.
The only other book I've read is Splinter Of The Mind's Eye. I enjoyed it also. Since it was commissioned by Lucas as the sequel to Star Wars, it has some familiar characters and themes, but it's also not bogged down by Lucas' tampering or universe shrinking.
