As he does with everything, Tolkien takes Romantic Fantasy to a whole other level. Indeed, the romance between Beren of the House of Bëor and Lúthien Tinúviel makes the tale of Aragorn and Arwen look tame.
"Among the tales of sorrow and of
ruin that came down to us from the darkness of those days there are yet
some in which amid weeping there is joy and under the shadow of death light that endures. And of these histories most fair still in the ears of the Elves is the tale of Beren and Lúthien." - J.R.R. Tolkien
(Tolkien often referred to his wife, Edith, as "my Luthien" – for the Elf maiden in question was inspired from her)