But the system leaves out those that aren't interested in a soap opera back story of information. It also does little to encourage a casual buyer to get any one book as they don't know whether they might need to get other books.
It doesn't leave them out if it's written in a way that they don't need the whole backstory to understand and enjoy the story at hand. Which it is.
There is room for more than just continuity works.
Yes, there is. And there are.
If they were not doing that when the shows were on, then it is part of the problem, over-arching continuity choking off creativity.
You're saying they should move away from continuity to not confuse newcomers, right? So how would it have helped newcomers who just watched the latest episode to read a novel that was written before the episode aired which turned out to contradict it?
If a writer really wanted to write something completely original, he wouldn't be doing tie-in fiction.
It doesn't matter what the writers want to do in this. This is a problem for the publishers.
...Wait, so you've gone from "embrace writer creativity" to "it doesn't matter what writers want to do"?