I'll start off by naming the tie-in pieces, and then moving to independent literature.
Tie-ins:
Star Wars
The Thrawn Trilogy, Timothy Zahn
This put Star Wars on the map again, way back in 1991. If not for this, there'd be no prequels. It introduced Mara Jade, who rules hardcore enough for her to eventually marry Luke. It also had Thrawn, who was pretty awesome in his own right; he definitely wasn't the despot that the Emperor was, but he almost castrated the New Republic. Compared to some of the later novels, it wasn't that deep, but its scope was very impressive, and it laid the foundation for basically all of what was to come, including large parts of the prequels, most notably the name of the capital planet. Zahn came up with the name Coruscant, which was far better than Lucas' original name (Had Abaddon); because of Zahn's influence, Lucas changed it to Coruscant for the prequels.
The Hand of Thrawn Duology, Timothy Zahn
Seem repetitive? It's not, really. It's Zahn's personal and well-written literary bitchslap to all the other authors who totally fucked up the characters. It features an Endor-sized battle at the end, the high adventure element of the movies, spying, and a lot of reflection, most of which is done by Luke and Mara. It also contains the long-awaited peace accord between Alliance and Empire, twenty years after the Battle of Yavin.
Traitor, Matt Stover
This book is awesome, no buts about it. It was written by Matt Stover, who's become one of my favorite authors. The entire book centers around Jacen Solo, who I hated with a passion prior to reading this. Basically, he gets tortured and mind-fucked by a Jedi of the Old Republic, Vergere, who ended up with the Yuuzhan Vong and teaches a Force doctrine that's like someone mixed objectivism, moral relativism, some scotch, and a nuclear warhead. It's hella philosophical, and it contains a lot of violence, humor, and UTTERLY DISTURBING SHIT. Even the cameo by the previously killed Anakin Solo is funny. Bear in mind that I was practically still in tears because they killed him, and then out of nowhere comes a giant LOL-hammer to smash me in the nuts. It even got me to like Jacen. If only the other authors had taken a cue from Stover. Hell, even KJA's rendition of him was better than some of the NJO authors' versions.
The Unifying Force, James Luceno
My favorite book in the Star Wars pantheon, and quite possibly my favorite period. It's the conclusion of the NJO, and features some uber-god Force antics, except unlike DBZ, this shit is actually awesome. It has not one, but two massive space battles in its pages, as well as the resolution to a lot of moral questions that had been raised by the series. It also finally gave a true farewell to Chewie and Anakin Solo. Oh yeah, and it had Kyle Katarn in it. Major props to Luceno for that. He managed to wrap up basically every plot strand in a nice, neat, and highly explosive package, and even managed to rectify some of the NJO's longstanding flaws that fans had been complaining about; some of this merely involved doing a better job of writing the characters. One example of this is his excellent rendition of Mara. His writing for the space battles also cleared up a lot of technical issues, and part of the ultimate ending involved a living planet. This book came out in 2003. Guess what was in the plot development stages at the time? Advent Children. I'm pretty sure they stole it from this, but hell, I'm not complaining.
Shatterpoint, Matt Stover
This novel set in the Clone Wars features Mace Windu. It's brutal, intense, gory, and deeply reflective. This was also written by Matt Stover, whose message equated to "war is hell." He did a convincing job of conveying that, especially in this scene where this random twelve-year old kid gets sliced in half.
Republic Commando: Hard Contact, Karen Traviss
This isn't just a Star Wars novel, it's a videogame tie-in, so it's a tie-in twice over. And guess what? It RULES. The author takes military tactics VERY seriously, as did the game developers. She got involved with the development of the Mandalorian language, Mando'a, which was used for the game and has been used in other Mandalorian-related materials. She even went to the trouble of referencing KOTOR's Canderous Ordo. The upcoming sequel, Triple Zero, is going to feature the squads both from the game and from the first novel, as well as the instructors and a descendant of Canderous'. Plus, it's going to be urban warfare on Coruscant. Could it GET any more promising?
The Unseen Queen, Troy Denning
I actually haven't read this yet, nor do I know anything about the series it's part of, aside from one thing: Jacen finally has a kid. I fear for the universe, but at the same time, it's now a proven fact that he isn't gay. It involves some very old Star Wars issues, some of which were crafted from the NJO era and some of which have been standing since its origin.
Other Science Fiction and Fantasy
The Lord of the Rings Saga, J.R.R. Tolkien
I'm including The Silmarillion with this, even though it's technically wrong to do so; they take place in the same universe, so blah. It was basically the first truly lasting modern epic. Notice that I use "modern" rather than contemporary; Star Wars takes the latter title. The only real issue I have with it is that I prefer to rely on my own effort rather than faith, though I'm pretty convinced that something's watching out for me, considering all the shit I've done that should have gotten me in trouble. I'm also unsure who to give credit for the Battle of Hoth scenario to. Jackson's visual depiction of the Battle of Pelennor Fields was clearly inspired by the Battle of Hoth, but on the other hand, Lord of the Rings came first. So who gets the credit?
The Once and Future King, T.H. White
OK, so I'm using this as a catchall for the Arthurian legend, but hell, it was pretty damned good, and basically the only required school reading that I ever liked.
Harry Potter and the Sorcerer's Stone, J.K. Rowling
I'm only giving props to this because it stopped me from eating about 50 other clarinetists last year, but it was pretty good. Though I don't find it cocaine-like as I do Star Wars, I can understand why a lot of people do.
The Odyssey, Homer
You've got to give props to the originals, much as the original Zelda often appears in "best n games" lists, but the fact is that this story is pretty good on its own merits. It's the origin of basically every staple of fantasy known to mankind: great beasts, gods, weird x-zones that fuck with your senses, and scantily clad chicks for no damned reason.
The Call of Cthulhu, H.P. Lovecraft
You'd be remiss if you didn't mention this, but especially on a Chrono forum; Cthulhu was much of Lavos' inspiration. It was freaking scary as hell, moreso than most of Edgar Allan Poe's stuff, at least to me. Cthulhu also served as the basis for Eternal Darkness' Ancients. They even admit this in the game with various veiled and open references to Lovecraft's works; often, when one examines bookcases in eras after Lovecraft's life, his works are present in great volume.
The Raven, Edgar Allan Poe
That said, this was awesome. It's a poem, but its fantastical elements cannot go unnoticed. Neither can its penchant for being made fun of. "Quoth the server, 404" indeed.
Babylon 5: Clark's Law, Jim Mortimore
Admittedly, a lot of the B5 novels have sucked atrociously, but this was a fantastic exception. Its character depictions were true to the show, and the original characters were highly engaging. Its central moral dilemma resonated with issues that people face today, including abortion, capital punishment, religion, cultural differences, and imperialism. It was gritty and had plenty of balls, and featured the wasting of planets and new perspectives on events related in the show. Some of the stuff doesn't adhere to canon, but it's good nonetheless, and arguably even better than what's featured on the show.
Babylon 5: The Passing of the Techno-mages, Jeanne Cavelos
This novel trilogy deals with the techno-mages, some of the most enigmatic beings in the B5 universe. They use highly exotic biotechnology to simulate the effects of classical magic. Basically, they can do everything you'd see in any given Final Fantasy, from firestorms to lightning bolts to levitation to Ultima-esque spells that ruin people's shit. One such spell figures centrally in its storyline. On a large enough scale, their tech could own nearly anything. The main character is Galen, the techno-mage character featured in the short-lived yet (IMO) underrated B5 spinoff Crusade. The techno-mages use a master-apprentice training situation similar to that of the Jedi, and Galen's master is depicted as being Elric, the first techno-mage ever to appear on the show, back during its second season. The trilogy's storyline was like Star Wars' NJO, in that it was the first to do something truly unconventional within its environs. But, as it was written by one author instead of many, its characterizations are more consistent. Interestingly, the author that wrote this also wrote The Science of Star Wars, which was a step on the way to Curtis Saxton's Technical Commentaries.
Misc.
Maddox's book
Well, he made it, so I'm preemptively putting it on my favorites list, because it's guaranteed to rule.
When Will Jesus Bring the Pork Chops?, George Carlin
George Carlin just rules. End of discussion.
Atlas Shrugged, Ayn Rand
Yeah, it's essentially an excuse to promote her philosophy, but at least her philosophy's a decent one.
The Physics of Star Trek, Lawrence Krauss
Classic book of science fiction analysis. It doesn't get much better than this.
A Brief History of Time, Stephen Hawking
This set the standard for all pop-science books. My favorite quote from it is where his publisher told him that for every equation he puts in, half his readers are scared off like little pussies. Absolutely priceless.
The Elegant Universe, Brian Greene
This is like A Brief History of Time: The Next Generation. Even though I have some beefs with string theory that I don't think have been explained well enough, the book does a good job of explaining it. Oh yeah, and its cover art utterly kicks ass.
America: The Book, Jon Stewart
This book is evil enough that my mom told me I was going to hell for reading it. Yeah, it's that good.
The Adventures of Huckleberry Finn, Samuel Clemens
I guess I'm one of the few people in my class that appreciated this book, but my class was full of faggoty buttfucking pussies. Mark Twain was EXTREME!