If you've always wanted to experience first-hand what's so enchanting about Skyrim but lacked sufficient funds, then we've a good news for you. The next free weekend game on Steam is The Elder Scrolls V: Skyrim Special Edition. That's the remastered version of the original Skyrim.
Get TES V: Skyrim SE here on Steam.
Note that it's not a free to keep offer (like recent Mirage: Arcane Warfare promotion). It can only be played for this weekend. Specifically, till 10PM PT on Sunday, September 10. After that one must buy it to play it.
Also, the game is on sale for 50% discount and will stay that way for less than a couple of weeks. So it definitely isn't a bad time to get into the world of Skyrim.