[Zigûr]

In Reading The Lord of the Rings Michael Drout makes comparable statements, suggesting caution when it comes to methods of reading which can "turn Tolkien into his own leading critic".

I like to think of the letters, essays and so on as part of a "corpus" with the main narratives, at least when they're adding to and/or offering commentary on those narratives. Thus I aim to read the letters and so on as part of a broader textual complex. Oddly enough, when I googled the phrase "textual complex" just then to see if it was a term I could meaningfully use, the sixth entry to come up was Drout's J.R.R. Tolkien Encyclopedia: Scholarship and Critical Assessment.

On the other hand I think there is also plenty of merit to reading the texts individually and in a certain degree of isolation. Both approaches can be enlightening.