A further thing I've found (haven't done any actual work on this because my PC was broke, almost fixed now)
If you use the interactive human based search on www.isbndb.com
it works amazing well and gives you a good prioritised list of results.
You stick in "title by author(s)" in the text box and wahay. Pity their API does not implement the richer search. I'm almost tempted to build a screen scraper for the html version of the site.