Top Tier:
I cherish the Thrawn Trilogy and personally consider it as the "de facto" Sequel Trilogy. I also love the "Dark Empire" Trilogy and generally consider that something like "Episodes X-XII", or like an alternate sequel trilogy. Most of the Marvel and "Classic" daily comics also are almost constantly in my EU thoughts.
Second Tier:
Splinter of the Mind's Eye (It's very great, but Vader's dialogue is pretty lame: "Girl-Woman")...It's greatest strength, and greatest flaw, is it's 1970s "Pre-ESB" continuity limitations, which renders it both charming and retroactively strange. The Han Solo books by Brian Daley are very adventurous and very fun, and I consider them perfectly part of canon and extremely enjoyable, yet sometimes they feel a bit atypical from Star Wars in general. Most of what I read from the pre-PT EU falls under the Second Tier, IMO. Of the PT and after era, I like the Dark Horse comics, and the Legacy series (despite its Prequelizations...which I tend to ignore...). Basically, these are very enjoyable books yet they are flawed with odd characterizations of beloved characters (everyone seems to get Luke slightly off...he's either a dumb-witted, wide-eyed formboy, or a godly Kenobi on steroids) or have elements that, to me, are somewhat "fishy" for what I would personally consider canon and all. For example, I highly enjoyed "Shadows of the Empire" and loved Xixor and all that, BUT it was noticeably lame to bring in a "Han-clone" (accept it Dash fans! haha) and for the unique time in which it was set, it failed to deliver the one HUGE thing I always wondered about in between ESB and ROTJ...as in...how did Luke finally become a full Jedi in that time span, since he definitely didn't see Yoda again before his death in ROTJ and he didn't seem to have seen Kenobi's ghost (according to the book)...what did he do to become a Jedi?!? Who made him one? Furthermore...I hated how they passed off Luke's clothing in ROTJ as simply something either Lando or Dash gave him once they went to Coruscant. Come on...we all know that was supposed to have been the Jedi warrior garb from their heyday... Things like these get odd, and there are way too many Post-ROTJ books from the 90s. Wow!
Third Tier:
The "Legacy of the Force", "Fate of the Jedi" 9 part book series, and all. I hate to say it, but I enjoyed a good deal of "LOTF", mostly because I imagined the whole thing as a series of "made for TV" movies and since they brought back Lumiya and were atleast entertaining. The death of Mara-Jade, the re-hashing of...the entire film saga, the "here and there" prequelisms, and Karen Travis....knocked that series down quite a bit. Nonetheless, when I did read them all, I was almost always entertained. FOTJ...I haven't read much of that, and I wonder if its any better (although my bet is on worse). Also, the "cream of the cream of the crop" (yes not a typo)...I mean the ultimate BEST of the PT books come out here, and, in my mind, the best of those are two works that come AFTER ROTS, which are "The Rise of Darth Vader" (or whatever that book was called) and the recent graphic novel "Darth Vader and the Lost Command". The former was very good (but it still had prequel shit in there) and the second had a very interesting similar "Vader in the beginning" setting, despite the strange animation and prequelisms from here to eternity.
Complete and Utter Trash:
The "Clone Wars" new TV series movie novelization and other similar books. Karen Travis's books outside of the (only slightly) palatable one's she did for LOTF. Almost any Prequel era book. Even ones I once enjoyed, like "Labyrinth of Evil" and "Dark Rendezvous" are unbearable to me now with how much I completely detest the Prequels now. Kids and Junior novels are in the same boat. "The Glove of Darth Vader"/"Jedi Prince" had some unique drawings and are so "retro" (relatively speaking) and so NON-prequelized I will give them a slight pass!