The Lays of Beleriand are epic stories in verse form of the Elder days of Middle-earth. Contained herein is The Lay of the Children of Hurin, which tell the tale of Turin Son of Hurin and Glorund the Dragon. The Lay of Leithian tells of Thingol, of the meeting of Beren and Luthien, and of the battle between Fiingolfin and Morgoth. Together these Lays form an important backdrop to The Silmarillion, and illuminate some of the oldest tales of Middle-earth.
"The Lay of Leithian" is the familiar story of Beren and Lúthien. The rhyming couplets are perfect for this story; I prefer it over all the other prose versions. It also has a lot more detail. "The Lay of the Children of Húrin" is in alliterative verse, and I enjoyed it, although maybe not as much. I don’t know a lot about poetry, but alliterative verse was a much better choice than rhyming couplets, since it’s a much darker story.
Least favorites: None of it is finished! Luckily we know how the stories end, but I would love to read them all the way through in verse.