Well, the book's code has to be looked up only once, when the Wikipedia article containing the book reference is written. For those books which don't already contain the LC code, determining it involves a 2 minute visit to the Library of Congress catalog's website.
Wow! the LC web site is much better than it was when I last tried this. I now agree that LC# is the way to go, if we have sites to look it up in.
Thanks, I'll check it out.