At the University of Michigan Library, in partnership with Google, we have been busily scanning our collections. This opens up lots of possibilities, including an exciting one that launches today: search the full text of a book from within Mirlyn, the library's catalog.
If a book has been scanned by Google, there is a "search in in this book" field within the library catalog record. Depending on the particular book, a search will result in full text results (if the book is in the public domain) or search-term only view (if the book is in copyright).
Here is an example of an out-of-copyright book (with full-text results available): 1931: A Glance at the Twentieth Century. The record in the catalog looks like this:
And here are the results of that search:
All books that have been scanned -- one million and counting -- are searchable. Search results are linked to the full text for those works that are in the public domain. Search results for books that are still under copyright are shown in brief view. Brief view displays a phrase or two on either side of the search term, but doesn't include full-text display of the page. In either case, the search in the book tool will help you know if you want to get the actual book off the shelf before you visit the library or make a delivery request.
Try these sample records:
Full-text: The Miscellaneous Writings of Lord Macaulay