The whole situation with the availability/distribution of the ROTK:CR is fairly bizzare. I remember back when it was first released, Best Buy said they wouldn't even be carrying it!
For those who haven't been able to find it yet, Doug Adams has given assurances that the set will not be allowed to disappear anytime soon. Even if Reprise Records mysteriously vanished off the face of the earth tomorrow, Howard Shore personally retains the rights to all the materials. So patience is the best virtue right now...
Doug's author's blog is a great source of info on all things LOTR music, BTW ( themusicofthelordoftheringsfilms.blogspot.com ). Lots of juicy tidbits there about the upcoming book and Rarities Archive (we're talking hours upon hours of demos, alternates, and never-before-heard extended and unused compositions -- tremendously exciting stuff).
My most serendipitous soundtrack find was at a classical music store that had a small used CD shelf. Someone had brought in mint copies of Accidental Tourist, Witches of Eastwick (before it was back in print) and Star Trek: The Motion Picture (before the expanded release). They were $7 each. I was fairly happy that day.
