Heeeey, I never expounded on my love for
The Road To Middle-Earth yet, did I? It's rare to get a glimpse at a great artist's creative process to begin with, so this is really a gold mine. It should be part of a big series IIRC, or at least I seem to remember several books on the subject. At least, that wasn't the cover when I rented it back in 2003.
Either in that book or a similar one, there's a passage about how Tolkien got all the way up to the gate of Moria in an early draft of
The Fellowship of the Ring, and then he realized:
Oh snap, I should have an Elf and a Dwarf in the party, shouldn't I? And that thought would forever affect Orlando Bloom's career decades later. Classic stuff.