Read Heir to the Empire, Dark Force Rising and The Last Command by Timothy Zahn.
That is the "Thrawn series," wherein the New Republic mops up the remnants of the Empire following ROTJ. Ripping good yarn.
Avoid New Jedi Order trash.
Anything by Kevin J. Anderson (Jedi Academy series) is passable. Darksaber is pretty entertaining, so are Tales from Jabbas Palace and Tales of the Bounty Hunters...and Tales from the Mos Eisley Cantina.
I personally love the Boba Fett trilogy by KW Jeter....lots of cool crimeworld stuff going on, explains how Fett survived the Sarlacc, etc.
Oh, and Shadows of the Empire is pretty awesome. Set between ESB and ROTJ. Xizor is incredibly cool.
Michael A. Stackpole writes pretty good stuff, too. Mostly about X-Wing pilots, I think.