What Galveston said.
If I have time, say months and months before Opening when a show is announced and I know it has source material that I'm interested in, I'll investigate before the show opens. If anything, I've occasionally passed on shows (or put them off if they're long-running) because I didn't know the source material and didn't want the show to color my opinion of the original. But people who go to Hugo or Leroux and expect Schönberg/Boublil or Webber (or Fellini or Bergman and expect Yeston or Sondheim, but I suspect appreciators of that set are more prepared for the originals) sadden me...
And anyone who goes to Stevenson or Orczy or Stoker or Carroll and expects Wildhorn is just trolling themselves.
Words don't deserve that kind of malarkey. They're innocent, neutral, precise, standing for this, describing that, meaning the other, so if you look after them you can build bridges across incomprehension and chaos. But when they get their corners knocked off, they're no good anymore…I don't think writers are sacred, but words are. They deserve respect. If you get the right ones in the right order, you can nudge the world a little.