If you’re opening up an online market and facing huge competitors like GameStop, eBay and Amazon, your only hope is to have a better user interface for buying and selling. That’s the thinking behind Glyde, an online market for used video games, CDs, DVDs, and books.

Fortunately, the big guys have kept the bar relatively low. On eBay, for instance, it can take as much as 77 clicks over 10 minutes to put one item up for sale. Simon Rothman, the former head of eBay Motors, thought that was ridiculous. So he started Glyde to make it much easier. Used games are a $4 billion market in the U.S., and Rothman wants a chunk of it.

With Glyde, you can start selling a video game almost immediately. You register once. Then you log in and click on selling. You start typing in the name of the game you want to sell. The autotext takes over and you can click yes if it guesses correctly. Then it suggests a price to you that is based on the average market value for that used game. You can set your price slightly lower than market if you want it to move fast. If the market value of a game drops below the price you’ve posted, Glyde sends you a notification so you can make an adjustment.

Then you’re done. You get an email if the game sells. Then Glyde mails you a package with the postage paid and address of the buyer. You stick the game in the envelope and drop it in the U.S. mail. When the buyer verifies that he or she got the game, Glyde will release the funds to you. It takes a 10 percent fee and a $1.25 fee for postage. On average, buyers can save 90 percent on prices for used games; sellers can get more than twice as much as they usually get by taking it into a store to swap it for store credit, Rothman said.

“The problem with used games is you over-pay or you get ripped off when you sell it,” Rothman said. “With us, you save money and spend as little time as possible.”

The savings and convenience are why Glyde has been able to grow from thousands of buyers and sellers to 350,000 in just five months. In the first quarter, the company tripled its revenue, and it now has millions of items for sale. That’s why the company is worth keeping an eye on, even though its competition includes Gamestop, Goozex, Barnes & Noble, Borders, eBay, Amazon, Switch Games, and Swaptree.

Rothman said Glyde’s simple selling system took a long time to build. He founded the company in 2006, brought in Excite co-founder Mark Wong-Van Haren as chief technology officer, and started selling last November with a beta site.

He was an early eBay employee and founded eBay Motors. He ran it for six years and grew it into a billion-dollar business.

With Glyde, they have paid attention to the details. You can sell a game in “new, excellent, and good” conditions. But you can also sell it “disc only.” That means Rothman can get as customers the tons of people who have lost the boxes to go with their games or DVDs. The buyers offer feedback; if you aren’t honest with your descriptions, the buyer doesn’t have to pay. Once payment is confirmed, Glyde credits the seller’s account. At any point, the seller can then transfer the balance into a bank account.

Rothman is hoping that gamers who like this system will sell more games than they otherwise might and make a lot more money doing it.

The wild card here is that the used game market has caused a lot of consternation in the game ecosystem. Game developers and publishers hate the used game market, since they don’t get a cut of the sales. Electronic Arts will begin to charge players with used games a $10 fee if they want to play online. But there isn’t much the game publishers can do about it right now. They are trying digital distribution through online players such as OnLive, but that may take time before it really catches on.

Glyde has raised $6 million in funding from Charles River Ventures. It has 15 employees.