The description from Board Game Geek is as follows:
Xia: Legends of a Drift System is a 3-5 player sandbox style competitive space adventure. Each player starts as a lowly but hopeful captain of a small starship.
Players fly their ships about the system, completing a variety of missions, exploring new sectors and battling other ships. Navigating hazardous environments, players choose to mine, salvage, or trade valuable cargo. Captains vie with each other for Titles, riches, and most importantly Fame.
The most adaptive, risk taking, and creative players will excel. One captain will rise above the others, surpassing mortality by becoming Legend!
Customize: Each player begins the game by choosing and customizing a Tier 1 starship. Invest all your money in engines and be a rapid, yet fragile, explorer. Put all your credits into an uber missile and watch other players flee in terror. Get a small engine and save space and credits to invest in buying and selling cargo. Or create a well rounded ship, ready for anything. In Xia, the choice is always yours.
Adapt: The goal of Xia is to become the most famous captain. Completing missions, besting ships in combat, purchasing higher tier ships, selling Cargo Cubes and claiming Titles are all ways that players can earn Fame Points. The best pilots will adapt to their surroundings, making snap judgments and changing plans on-the-fly. If you can think on your feet, you'll do well in Xia!
Sandbox: The real fun of Xia is that each game will be different. There is no set direction of play, players may choose to be peaceful traders, fierce pirates, workers, miners, opportunists, etc. The game board is randomly laid out and explored each time you play. Players might choose not to explore at all, creating a tiny arena for swift and deadly combat, or explore all 19 sectors and have a large play-scape to exploit. It's up to you!
Some folks think this game is too long. I feel I could play this game for many hours, even making a whole day of it. 4X games (eXplore, eXpand, eXploit, and eXterminate) that have a wargamey feel, particularly Science Fiction themed games with space combat, are particularly enjoyable to me. Xia is fairly close to that type of game except you don't control an empire, just a single ship. Upgrading the ship, exploiting new trade routes, exploring an expanding territory, and exterminating your opponents are all equally important in Xia. It's a top notch game with tons of replayability.