The service will carry new indie games, beginning today (March 27) with puzzle platformer Trine and adventure game The Whispered World.
GOG will also take pre-orders for new titles prior to their release - the first of which is indie role-playing game Legend of Grimrock, to be released on April 11.
Other titles such as Spacechem, Machinarium and Darwinia will also be releasing soon, with over 20 new and indie games scheduled over the next few months.
All new games distributed through GOG will be DRM-free, as all games on the service have been since it began.
The addition of new games accompanies a site relaunch featuring a more modern layout, searching without a user's own account and more organisation options for a user's game library.
A new GOG.com downloader will also allow faster downloads and makes downloading patches easier.
Last year, GOG reached 6 million downloads for the service's third anniversary.
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Watch the launch trailer for Legend of Grimrock below: