The History of Middle-earth
He called his collection of nascent stories "The Book of Lost Tales". This became the name for the first two volumes of "The History of Middle-earth", which include these early texts. Tolkien never completed "The Book of Lost Tales"; he left it to compose the poems "The Lay of Leithian" (in 1925) and "The Lay of the Children of Húrin" (possibly as early as 1918).