Interesting thread here. To add my 2p, I'd say that Greg and Chris hit the marks regarding the "rules". At the end of the day, the tie-in writer must
serve the source material over all other concerns - even if
that source material contradicts itself, other tie-ins or goes on to contradict the work being written. Generally speaking, screen trumps paper
Of course, a good writer will try to ensure that their tie-in work doesn't ride roughshod over other tie-in works in the same sphere (and if they do, the line editor should pull them up about it!), but that's often down to the writer to police those details.
Admiral Rex wrote:
Why do Star Trek and Star Wars fans think that all media must tie into a single, consistent continuity?
Check out Doctor Who
fandom; many of those guys have tied themselves in timey-wimey knots trying to create a coherent continuty from the many differing elements of that mythos...