All of Western thought may be footnote to Plato, but all Western fantasy is a footnote to Tolkien. A "new' book by Tolkien certainly is welcome, and it's interesting to be confronted by his somewhat staggering limitations as a novelist.
After reading the introduction by Chris Tolkien, JRR's editor/son, I learned that this story was severally written as alliterative verse, a lay, several snippets of notes, outlines, etc, and smoothed together later. It's episodic, and ends on an extremely down note. Which is great! I love a bummer! It's not like he didn't warn you! Muhahaha!
There's some odd, glancing stuff in there too: a carpenter and a throne project that will never be completed, weird petty dwarves, a nice description of a swirling waterfall and it's connection to the sea. But hey, it's Tolkien, if you don't already love it, curse you to the pits of Morgoth.