I've been thinking about this some more over the past few days, and I do still prefer a split with Silmarillion and LOTR book separate from each other, as well as books separate from movies. (I don't have strong feelings on how the movies are split/combined or how The Hobbit is handled.) The Silmarillion and LOTR are set far apart in time (up to thousands of years) and in a different physical setting, and not all fans of one are familiar with the other. On the whole, it makes more sense to me to keep them separate. But I can deal if you combine Silm and the LOTR book.

Thank you for popping back! It's definitely helpful to gauge the people's full opinions. Based on the comments so far I'm definitely going to split books/movies and it seems combining the movies will work best. So the options we're then whittled down to now are (though I welcome feedback on better umbrella fandom tag names if people have preferences, I haven't combed through the AO3 tag tree to see if there's an existing option we could utilise yet):

Tolkien - All Books
Jackson Movies

OR

Silmarillion
Tolkien - LotR and Hobbit
Jackson Movies

At this point it does still sound like the books meet the shared universe requirements which other fandoms do, but I'm hoping a few more people might weigh in before we make a decision as I'm aware there are strong opinions involved.

Can you clarify the time issue for me? Someone else said they want to request characters who technically appear in both LotR and Silm but they only want one backstory. A brief Silmarillion for Idiots 101 is welcome if you think it'll support keeping them separate, I'm happy to be over-explained to if it means I don't miss nuances that might be important and aren't obvious to me - is it just that the Silm covers such a long period of time that some characters are Silm only and some characters later in that time period thus will be/are still alive in LotR?

And for characters that do appear in both: is it the same character (just with omissions of backstory if you don't want to read them all), or are there other differences in backstory between books that I'm missing?

Okay. This is kind of complicated. If you ask "Are The Silmarillion and The Lord of the Rings one continuity?" the answer is that they are and they aren't. It wasn't as simple as him writing one book and then the other.

The Lord of the Rings was published during Tolkien's lifetime, in the form that he wanted. The Silmarillion was compiled after Tolkien's death by his son, Christopher Tolkien, from Tolkien's notes, decades later. The thing is that Tolkien never stopped rewriting and changing his mind about things. The Silmarillion is Christopher Tolkien's best guess at what his father intended, plus whatever was complete enough to be made into a coherent story. Christopher was not entirely satisfied with the published Silmarillion as a complete snapshot of his father's work, so he started publishing more volumes of JRR Tolkien's notes and fragments about Middle-earth. This became the 12-volume History of Middle-earth series plus things like The Children of Hurin, Unfinished Tales, etc. And the Silmarillion tag on AO3 intentionally covers all of that mess, because it's "The Silmarillion and other histories of Middle-earth." If you look at all the material, you're going to get multiple contradictory versions of various characters' motivations, backstories, parentage, details of characterization . . . To take one infamous example, if you ask a Tolkien fan who Gil-galad's father is, they'll laugh ruefully, because Tolkien changed his mind about that like six different times. Or they'll tell you which version they personally prefer.

And fans have different ways of approaching this complex and contradictory morass of material. Some people have only read The Lord of the Rings. Some have read The Lord of the Rings and the published Silmarillion. And some have read LOTR, the published Silm, and some or all of the other volumes of notes.

(My internet is being buggy, so I'm going to post this much and continue in further comment(s).)

(And of course even among people who have read some or all of the Histories of Middle-earth stuff, there's a range of decisions about how much they choose to incorporate it in their fanfic and meta, from "lots" to "not at all.")

Every other exchange I can think of separates LOTR and the Silmarillion. I would say that combining them is not the most intuitive thing to do. It might seem from an outside perspective that they're the same thing, because they're set in the same world with some of the same characters, but there are also some significant differences. The Silmarillion and The Lord of the Rings are written in very different styles. The Silm is written in a detached chronicle-style, with relatively little dialogue, covering thousands of years, including creation myths and accounts of the gods; LOTR is a novel (or series of novels, depending how you look at it) with normal dialogue and getting into the characters' heads in the way you'd expect from a modern work. Not everyone who is interested in one is interested in the other. Combining them might be logical from a shared-world perspective, but I'm not sure that it serves the fans.

As far as time periods go, The Silmarillion takes place over thousands of years, and then LOTR takes place ~3000 years after that (that's over-simplifying slightly, but close enough). Some of the characters from the Silmarillion are still alive in the later time period of LOTR, because they're immortals of various kinds (they can be killed but they don't die of old age). Most of the places mentioned in the Silm are destroyed by the end (a large part of the continent becomes covered by the ocean), so LOTR takes place almost entirely in different geographical locations and set in the cultures that have sprung up in the intervening time. So writing LOTR fic and writing Silmfic is, in most cases, in a different geographical/cultural context (and again, not everyone who is interested in one is interested in the other).

So, is Galadriel in LOTR and Galadriel in the Silmarillion the same character? Well, she's the same person, because Tolkien says she is. But you'd get a different characterization from someone who is taking her Silmarillion backstory into account and someone who isn't. For example, just from reading LOTR, you wouldn't know that Galadriel had four ( . . . or three, Tolkien changed his mind) brothers, one of whom was killed by Sauron -- which makes her fighting Sauron throughout LOTR a bit more personal. Galadriel's decision to reject power, return into the West and reconcile with the gods in LOTR means a lot more if you know from the Silmarillion that she originally came to Middle-earth as the result of defying the gods and wanting to have a kingdom of her own. So it isn't only a matter of facts and events; there's hundreds or thousands of years' worth of stuff that add resonance and motivation to what she does in LOTR. If you request or offer the Silmarillion in an exchange, you can assume that everyone's working with the same background. If Silm and LOTR are combined, that's no longer a safe assumption. So yes, they're the same characters, but "same" becomes not really the same when someone who has only read LOTR is (from the perspective of a Silmarillion fan) missing a lot of context for those specific characters. I think that's what people mean when they talk about wanting a LOTR/Silm character with her Silmarillion backstory. Also, Galadriel as portrayed in the Silmarillion is more, I don't know, feisty? She's mellowed a bit by the time of LOTR. And both sides of her are part of her character, but it you only read LOTR, you only get one side. Basically, I would expect different things from requesting/offering Galadriel in the Silmarillion vs. requesting/offering her in LOTR.

I'm talking about this from the perspective of a Silmarillion fan, who does want to play around with the additional material. There are a lot of Tolkien fans who haven't read the Silmarillion, and that's totally fine! And from their perspective, I suspect combining LOTR and the Silm would be off-putting because it implies that you do have to take the thousands of years of backstory into account for characters who appear in both, when that's not something they're interested in digging into. I just feel that separating LOTR and the Silm gives everyone the most room to work in the particular context(s) they enjoy and avoid mismatch of expectations.

/my two cents

I'm just quickly flying through so this is brief, but I wanted to say thank you for taking the time to write me an idiots guide. From outside it does look more simple, and the changing canon continuities thing is I think particularly relevant to our combining/splitting criteria and it's not something I'd encountered browsing wikis in the past.

I'm guessing if you've got issues about eg. Gil-galad's father even just within Silm, then chances are some parts of Silm agree with LotR/Hobbit and some disagree?

I'll leave it open for discussion in case there's other (for me) unknowns and nuances that may come to light. But it sounds like Silm/LotR and Hobbit books/Jackson movies would be a better split, than combining all the books. Thank you again!