Unfinished Tales is probably my very favourite among the many wonderful books collecting his unpublished father's works that Christopher Tolkien edited over a span of more than forty years.
The audiobook version of Unfinished Tales was issued just last week; and I began listening on the day it was published!
It was a sheer delight to hear it read by the Father-Son duo of Timothy and Samuel West; whose versions of Beren and Luthien and The fall of Gondolin gave me so much pleasure.
Timothy W. takes the 'role' of Christopher Tolkien by reading the editorial material; while Samuel reads the main texts written by JRRT.
Timothy W. adopts an avuncular and relaxed persona; while Samuel reads with sustained concentration, tremendous intensity, and a focus on detail that could not be surpassed.
Consequently, although I have re-read Unfinished Tales many times, I became aware of many aspects - specific facts and general tone - that I had previously not noticed. This is one reason why I appreciate audiobooks so much - the other is my spontaneous enjoyment of hearing favourite words spoken aloud so well.
If you love The Lord of the Rings but have never begun to explore Tolkien's writings unpublished in his lifetime; this is where I would recommend you start - perhaps by listening to the Audiobook first, and then getting a paper copy for future reference.
You will hear On the coming of Tuor to Gondolin - the very best and noblest story of the elder days (according to Christopher Tolkien, endorsed by me!).
You will hear of Aldarion and Erendis and discover much concerning the earthly paradise of Numenor (this was Tolkien's only 'love story', albeit a sad one).
You will hear the 'back story' to The Hobbit as told by Gandalf; also much on the finding of the One Ring and the about the Nazgul.
I was (literally!) entranced by the information about the elves in general, and Galadriel in particular - hearing this vividly re-awoke the elvish fascination I first felt in my middle teens.
And there is much else concerning the five wizards - including the occasion when Gandalf first irritated, and then incensed, Saruman by smoking pipeweed, while Saruman tried to ply his rhetorical persuasion on The White Council... And of Saruman's subsequent guilty and secretive adoption of the pastime.
In short - the Unfinished Tales audiobook is a treasure trove for the Tolkien-lover. This was just the first of what will surely be many listenings...