Similar to Wookiepedia's layout, I propose a "Sources" heading section below "Appearances". The Sources section includes all non-fiction canon material such as Encyclopedias, Guides, Visual Dictionaries, etc.
With Ezio being arguably the most notable and popular AC character he'd have the most sources attributed to him. This example is most likely the one with the most sources. Another reason why I'd think its necessary is that if we make the Sources section and put all non-fiction material a character appears in, someone could then chase up additional information on a character using the sources. Wookiepedia's Sources section is hella in depth, and I doubt ours will ever get to that point. That would be when it would be considered cluttered, as shown above – this would be our most 'cluttered' Sources section but only because Ezio would have more non-fiction sources attributed to him.
I don't think we've really used our References as something other than a source list. Typically we use the <ref> tags as citations for where information comes from, and the citation-needed templates point to filling that in.
I'm not sure if this is strictly necessary, but have no qualms against this. I understand the point is to have the equivalent of an Appearances section for things that aren't appearances, i.e. things that don't have a narrative to appear in, and for that purpose I don't disagree with its inclusion.
It's slight extra work for people that have the non-fiction books (I have none -_-), but given it's literally just a list, sign me up for a tentative aye, barring some heavy objections from others.
I really don't see the need for having another list. I wouldn't categorize these sources to show what's fiction and what's not, I'd rather put everything in the list keeping the "references" as the section's title, identifying those fictional with the word "fictional" between parenthesis in italic (meaning that these documents, books, data pages, etc. have a place in the AC universe).
I'm not against it, but I don't see it totally necessary, IMO.
Agreed with Cristy's view on this. The games and the books are considered sources as well so I don't see why there's a need to differentiate whether they are fiction or non-fiction. This and the Appearances both essentially function the same thing so I suppose this issue can be solved if we include those books under appearances as well? Otherwise, we can stick to the current format since these books references can simply be found in the References section.
I would feel remiss to not support this as I find it similar to the Trivia vs BtS issue that I'm slowly (very slowly) working on. Maybe "Sources" can be renamed to something else to better show the IU vs OoU split from "Appearances".
I'm for it (and behind the scenes instead of trivia sections). It's not so much fiction and non-fiction but Appearances for stories and Sources for reference books. I'd consider the defunct Abstergo website or Handbook the latter when they're still presented from an in-universe perspective.