Tolkien Canon

When two Tolkien references differ in details, which details do you choose to portray?

Specifically, I adore the detailed and imaginative descriptions that J.R.R. Tolkien wrote in "The Book of Lost Tales".  They often amplify but sometimes differ in detail from his better-known "The Silmarillion".  Both books (and many others) were edited by Christopher Tolkien and published posthumously.  Both carry about the same authority because they're largely JRRT's own writing, but he didn't finalize either one of them.  Thus, neither is quite "canon Tolkien". 

 "Canon" (from the Greek kanon "rule") is defined

1. a general law, rule, principle, or criterion by which something is judged.

2.

 a collection or list of sacred books accepted as genuine

     3. the works of a particular author or artist that are recognized as genuine.

The two works JRRT published in his own life-time are recognized as canon:  The Hobbit and The Lord of the Rings trilogy.  While reenacting some events of "THE WAR FOR THE SAKE OF THE ELVES" told in both Sil and BOLT but not TH or LOTR, we must guess what would JRRT have written, had he written it out in full.

Happily, we have an example of that:  The last two pages of the 365 page-long Silmarillion collection tell all of Hobbit and LOTR.  Comparing the Silmarillion version and a canon version of the same story gives us what JRRT left out of "The Silmarillion":  Hobbiton, Sam's name,  Merry and Pippin,  all the families from Boffinses to Proudfoots, and that's just the first chapter.   Bilbo's name didn't make it to Silmarillion, even though he's the main character in the already-published The Hobbit,  and illustrates other differing details:  In Hobbit, Bilbo is fleeing goblins when he finds the One Ring; in Silmarillion, he's "a wanderer fleeing orcs"  These omissions and discrepancies are understandable: the Silmarillion is not a complete novel, but an outline of potential stories.  So "it's not in Silmarillion" is a bad reason to exclude people, places, and things that JRRT wrote about elsewhere. 

Discrepancies

In real life, factual accounts vary from witness to witness.  Ancient history is filled with guesses.   Modern history and news omit much.   It might be impossible to ever find the real "truth" of some real events, and even more impossible for fictional ones.  Like all authors, JRRT changed his mind about details.  He admitted sometimes that he forgot things then wrote something else in a later draft.
 

There are in-character reasons for discrepancies. The Silmarillion's lack of detail might be because the elves knew none of the details of the war for the sake of the elves.   They could not write about it unless the Valar had told them about it.  In BOLT,  a tourist hears the story from an ancient elf-princess who admits that even many elves do not know this history.  The ainu who might tell the elves what happened would differ in their tales, and not just because eye-witnesses accounts differ:  Aulë hides the truth when it suits him, Lorien distorts facts for fun, and Vairë says little but weaves pretty pictures.  The elves (and we) might never get the whole, consistent truth from them.

When bringing in non-canon elements that conflict or contradict, which do you choose to portray? Ultimately, "what is canon", like "WHAT IS TRUE"  seems to be an artistic question without an ultimate answer.   If you're exploring  literature, why choose at all?   Explore the ideas and versions and compare them. You'll enjoy the process and learn some things on the way.