Not long after, Beren is killed and Luthien mourns her lover with a grief so deep that her immortality breaks and she too dies. Mandar (keeper of the house of the dead) is so greatly moved that he returns life to the lovers who both live a long life and die natural deaths.
The second tale (much like the first) is most well-known thanks to The Lord Of The Rings movies--being the love story of Aragorn and Arwen. Some critics say the story of Beren and Luthien was the model for Aragorn and Arwen's story but one might consider the evidence that shows such a fantastic love story occuring twice in Tolkien's long history. After all, it is fantasy.
My understanding is that a stand-alone book telling the tale of Beren and Luthien will be released May of 2017.