1. The Thrawn Trilogy (Heir To The Empire, Dark Force Rising, The Last Command)
This recommendation is bittersweet in that while it's a great addition to Star Wars lore, it's probably going to be rendered non-canon with the release Star Wars Episode VII, which will also take place after "Return of the Jedi." Still, that shouldn't stop fans from reading the trilogy that not only reignited interest in Star Wars almost a decade after the last movie came out, but kickstarted the Star Wars Expanded Universe into what it is today. Taking place four years after "Return of the Jedi," Luke, Han, Leia, and all of our favorite former rebels are rebuilding the Republic and cleaning up trace resistance left of the Empire. From the edges of the galaxy, however, rises Thrawn, one of Palpatine's former Grand Admirals and newly appointed leader of the Empire's remnants. Recruiting the insane Jedi clone Joruus C'Baoth, Thrawn implements his intricate plan and sets out to defeat the New Republic and bring the Empire back into power. This book introduced many characters that became staples in the Star Wars Expanded Universe, like smuggler Talon Karrde and Luke Skywalker's future wife Mara Jade. As for Thrawn himself, he is perhaps the most famous Expanded Universe character and one of the best Star Wars villain in general. For those who have read this trilogy and want more Thrawn, I suggest reading the "Hand of Thrawn" duology, which takes place three years later. There's also the book "Outbound Flight," which takes place five years after "The Phantom Menace" and shows us what Thrawn was up to before he joined the Empire. Probably the most important series to come out of the Expanded Universe, this trilogy should not be missed.