I've always strongly associated the works of Jack Vance with those of Gary Gygax. Not only did D&D's co-creator readily admit to the huge debt the game owed to those works, but I hear Vancian echoes in the cadences of High Gygaxian. Gary was flattered by such comparisons, given his great regard for the author of The Dying Earth, but felt his own unique writing style couldn't hold a candle to that of Vance. Even so, these two writers had many points of commonality, not least of all their liking for roguish characters and appreciation for sardonic humor (a trait they also shared with Clark Ashton Smith).
These points of commonality are particularly in evidence in The Eyes of the Overworld, the 1966 novel that introduces Cugel the Clever, perhaps the best known character from The Dying Earth series. Cugel is a silver-tongued thief, who fancies himself a member of the natural aristocracy, a man whose intellect and refinements are far above those of most other men, thereby entitling him to anything his wits can win, regardless of the means by which they do so. Of course, Cugel is no such thing, being at best a semi-successful con man, brigand, and philanderer who falls prey to the wiles of others at least as often as the reverse. And therein lies the character's charm -- his fallibility. Cugel is certainly far from a hero, as his often despicable actions make plain, but neither is he an admirable anti-hero, a character whom we respect precisely because he challenges the status quo. Cugel is, in my opinion, a very human character and his vicissitudes are generally self-inflicted, brought on by a combination of bravado and concupiscence; he suffers as much as he benefits from his trickery. To call him a "lovable rogue" is not to do him proper justice, but the phrase will have to suffice as short hand for describing just why I was attracted to rather than repulsed by Cugel.
The Eyes of the Overworld is a Picaresque novel that follows Cugel on a quest to find an item called an Eye of the Overworld. The Eye is a magical purple gemstone that, when worn as part of a pair, provides the wearer with a sublime vision of the world, one that turns shacks into mansions and hags into goddesses. Cugel must find the Eye as part of a bargain with the powerful wizard Iucounu, into whose home he had broken and by whom he'd been caught. Rather than slay the would-be burglar, Iucounu places an alien being inside Cugel's body. This creature, called Firx, possesses many hook-like appendages with which he can internally "encourage" Cugel to keep his mind on his appointed task. The wizard then sends Cugel to a far-away land and the main plot of the novel begins, with Cugel simultaneously trying to undertake his mission and extricate himself from it. While doing so, he encounters many amusing characters, strange sights, and demonstrates again and again that he is neither respectable nor trustworthy -- nor as clever as he believes himself to be.
Cugel, along with the Gray Mouser, was almost certainly one of the inspirations behind the thief character class. Reading this book gives one a slightly different perspective on the thief. Cugel may be a lovable in some sense, but Vance never lets the reader forget that he's also a selfish, lying coward whose greed, lust, and general viciousness rain misfortune down upon him as much as those he swindles. The Eyes of the Overworld is too humorous to merit being called "dark" and yet there is more than a touch of darkness to it, as there often is with Vance's best works. I think that's part of its appeal: it superbly juxtaposes wit and moral turpitude in ways that provide genuine insight into the baser natures of human beings, all the while never forgetting that it's a fantasy adventure story whose primary purpose is to entertain. It's rare to find an author able to produce a novel of this sort, especially one that isn't "heavy" or didactic, while being humorous, but Vance has done so and I appreciate it greatly.