The Return of the King is written by J.R.R. TolkienJ.R.R. Tolkien wrote The Silmarillion
[Human]: Some of my colleagues are raving about The Return of the King. Should I read it too?  [Assistant]: Yes, in my opinion anything by J.R.R Tolkien is worth a read, especially if you like the fantasy genre. [Human]: That's almost a cult like following for this author. I am a novice in this genre. Should I start with this book? Seems like a sequel ?  
Actually, The Return of the King is the last book in the series. You should start with that one so that you'll have a clear understanding of the series from the beginning.