This may be a side issue to the main issue, but I frequently try to research old titles that might be public domain, or might not.
One terribly confusing thing is that publishers frequently release “new editions” with trivial post-1922 changes/additions to pre-1922 works. It is often a bear trying to figure out on the basis of WorldCat entries and commercial services like Amazon.com what the actual copyright registration date is for many works at the 1922 border. It often is time-consuming to figure out which editions are “definitive” or “incomplete.”
As an example of what I mean, try to figure out the registration date of William Gerhardie’s Futility, a great 1920’s work. There are “editions” from 1991 and 1974 of the work which was first published in 1922. Through interlibrary loan and supplemental research, I will probably be able to figure which edition is the authoritative edition. But it takes a lot of time. I hope that one ancillary benefit of a google/library partnership is to make it easier to access such “metadata” or to compare editions of the same work. That would be a big win for consumers, google and libraries and project gutenburg.
BTW, I hope to resolve the Futility problems and scan/upload this work (in some form to Project Gutenburg soon).