Chances are good that, if you read Dragon during the Silver Age, you remember Skyrealms of Jorune. You never played it, of course -- I'm not sure anyone ever did -- but you certainly remember it, because it was advertised heavily in the pages of the magazine and those ads were really intriguing. I myself never even saw a copy of Jorune until sometime in the mid-90s, well after the game was first published (in 1985, I believe). When I finally did see it, I immediately understood both why the game seemed so intriguing in those ads and why I'd never met anyone who'd actually played it: an exotic, imaginative setting that employed a few too many made-up words to describe itself mated to an uninspired, clunky rules system -- a story all too common in the annals of the hobby.
By most accounts, Skyrealms of Jorune began its existence as a hack of Metamorphosis Alpha, the precursor to Gamma World. I can certainly see the connection, although the published version of Jorune presented a much more complex setting than did its source material. Jorune is the name of the first extrasolar planet humanity discovered, home to a variety of strange creatures, including the intelligent shanthas. The shanthas were at a Stone Age technological level when humanity first arrived to explore the world. The two species nevertheless negotiated treaties to allow for limited colonization by mankind. When a cataclysmic war cut the human colonists off from Earth and its supplies, possibly forever, they abrogated their treaties with the shanthas and seized more of Jorune and its resources than they were allowed by treaty. The shanthas retaliated by using a powerful force known as isho -- a strange energy field that permeates Jorune, amplified by its crystal core and which some races can tap into to create "magical" effects. Together, the humans and shanthas nearly destroyed one another and devastated the planet, leading to a millenia-long dark age that saw technology and society collapse.
The game takes place long after the war, once humanity has dragged itself back up to Medieval/Renaissance level of technology and social structure. The PCs are assumed to be humans (or one of two descendant races), seeking to become citizens of the main human state, called Burdoth. To become a citizen, one must impress enough current citizens in order to get them to sponsor you -- and one impresses them by doing all manner of errands for them, thus creating a good excuse for adventures. Jorune provides a good basis for many types of adventures, from seeking out lost Earth technology to exploring the wilderness to learning how to better manipulate isho and more. It's all very well done in my opinion, hampered somewhat by its presentation and by the fact that there's just so much going on that one can easily lose the forest for the trees.
Rules-wise, Skyrealms of Jorune was very much in keeping with Sliver Age sensibilities. It combined aspects of random rolls with player choice (such as swapping ability scores, for example) and used skills rather than character classes. Combat was complex, as were the mechanics of wielding isho. There were lots of charts and tables to consult, which contributed to the sense that Jorune was a fiddly, unnecessarily complicated game. The irony is that, while its rules were clunky, the designers seemed to expect that the game would focus more on "social" conflicts and exploration rather than combat and magical duels, if the referee's advice in the Sholari Guide is any indication.
In retrospect, Skyrealms of Jorune reminds me a lot of Empire of the Petal Throne, a game I've grown to like a great deal as I've had more exposure to it. Both focus on human descendants of interplanetary colonists whose civilization has regressed technologically and now must contend with an alien world populated by dangerous creatures and where "magic" is possible. Both even assume the PCs are unlettered bumpkins seeking citizenship as the framing device for adventuring. And both are hampered in the eyes of many by their detail and use of unfamiliar terms/languages to present their setting. I think this is a pity in both cases, but especially so in the case of Jorune, which seems not be as widely recognized for its creativity as is Professor Barker's creation. For all its faults, Skyrealms of Jorune is a memorable example of Silver Age RPG design and it deserves to be remembered.