Everyone's taste is different. Of all the Star Wars books I've read there is only a small handful I've really enjoyed. The rest I read just for understanding and information on the Star Wars universe. The following titles though, were really well done and got outside the cliched trappings of what they're selling us these days.
Darth Maul: Shadow Hunter, Michael Reaves - This isn't the greatest plot or writing, but the clean exhibition of Darth Maul's prowess is well worth it.
Shatterpoint, Matt Stover - Mace Windu flexes big time in this.
Star Wars Episode III: Revenge of the Sith, Matt Stover - Yoda lost to Sidious? The controversy will never end.
The Adventures of Lando Calrissian, L. Neil Smith - Old school Star Wars fiction prior to most of the established EU canon. Very different feel to Star Wars and will help you see how bad and repetitive many of the contemporary titles are. (Like you didn't know already.)
The Adventures of Han Solo, Brian Daley - See above.
Traitor, Matt Stover - If you're not on a mission to read every Star Wars book out there, skip everything before and after this novel in the NJO series. Read a primer somewhere of the Vong war so you have some context for this and enjoy Jacen's suffering.
There may be a few more I'm neglecting, but these were stand-outs to me at least. This list isn't definitive by any means, but you might really enjoy one or two of them.
You'll notice I skipped Timothy Zahn. Many seem to worship this guy, but I just don't care for him all that much.
Another novel I'd recommend is Darth Bane: Path of Destruction. I found it has a very in-depth look into the Dark Side of the Force and the mentality of those who read it, other than being quite well-written.
Outbound Flight is also quite good. Unless you are a fan of the Chiss and already know everything about them, the book makes you want to learn more about these outlandish people.
I agree Korroth, its excellent. Another book I find enjoyable is Dark Saber by Kevin Anderson. The Plot line is slightly far fetched but it is really well written.
I enjoyed the book Betrayal.
I liked the torture scenes from "Traitor". The way Vergere speaks is awfully interesting! I would be immediately punched if I spoke like her in RL, especially in front of my girlfriend.
I vote for the "Path of Destruction" too. It describes the way of the dark side in detail. Especially the first half, Bane's dark emotions, rituals and training in Sith Temple is nice.
I would say its sequel "Rule of Two" was also nice. Bane's scene was less appeared, but the concept of the Dark Side was described from his apprentice Darth Zannah. I like the way she uses the Force. By the way, it seems to be decided that the third novel of Darth Bane will be published.
Of course, "Revenge of the Sith" is nice. Not only Anakin's struggles, Dooku and Sidious's manipulating game, there are many Sith going on. Also Jedi side, Yoda, Obi-wan, and even Qui-gon, strong Jedi fighting with Sith. There were some philosophies I learned.
I like the "Betrayal" when it goes to the tassel and Vectivus's apartment. Lumiya was acting like small Vergere to lure Jacen into the Dark Side. But whole the legacy of the Force series, I don't feel any strong characters driving the story. That is something I wanted to see.