Another perennial favorite of mine, and a great end to a great trilogy. I think that the split between the storylines works better in this book than the last one, keeping the reader in suspense about Sam and Frodo's Quest but telling their story before the other one ends. 
I think that Tolkien made a great decision in including the Scouring of the Shire, forcing reality onto the vision of homely comforts which sustained the Hobbits through the deprivations of their adventures. 
The melancholy, bitter-sweet ending of the Grey Havens is the perfect conclusion not only to this book, but to the overarching themes of consequence and the importance of the preservation of culture and of history established throughout the trilogy.