The Silmarillion is the core of J.R.R. Tolkien’s imaginative writing, a collection of narratives ranging in time from the Elder Days of Middle-earth, through the Second Age and the rise of Sauron, to the end of the War of the Ring.
They are set in an age when Morgoth, the first Dark Lord, dwelt in Middle-earth, and the Elves made war upon him in his impenetrable fortress in Angband for the recovery of the Silmarils, three jewels containing the last remaining pure light of Valinor, seized by Morgoth and set in his iron crown.
Accompanying these tales are several shorter works. The Ainulindalë is a myth of the Creation and in the Valaquenta the nature and powers of the gods is described. The Akallabêth recounts the downfall of the great island kingdom of Númenor at the end of the Second Age and Of the Rings of Power tells of the great events at the end of the Third Age, as told in The Lord of the Rings.
Tolkien could not publish The Silmarillion in his lifetime, as it grew with him, so he would leave it to his son, Christopher, to edit the work from many manuscripts and bring his father’s great vision to publishable form, so completing the literary achievement of a lifetime.