Hi,

to examine the usability of Google's book viewability API when lookup
is done via ISBN, we did some experiments, the results of which I'd
like to share. [1]

For 1000 randomly drawn ISBN from 3,192,809 ISBN extracted from a
snapshot of LoC's records [2], Google Books returned results for 852
ISBN.  We then downloaded the page that was referred to in the
"info_url" parameter of the response (which is the "About" page Google
provides) for each result.

To examine whether Google retrieved the correct book, we checked if
the Info page contained the ISBN for which we'd searched. 815 out of
852 contained the same ISBN. 37 results referred to a different ISBN
than the one searched for.  We examined the 37 results manually: 33
referred to a different edition of the book whose ISBN was used to
search, as judged by comparing author/title information with OCLC's
xISBN service. (We compared the author/title returned by xISBN with
the author/title listed on Google's book information page.)  4 records
appeared to be misindexed.

I found the results (85.2% recall and >99% precision, if you allow for
the ISBN substitution; with a 3.1% margin of error) surprisingly high.

 - Godmar

[1] http://top.cs.vt.edu/~gback/gbs-accuracy-study/
[2] http://www.archive.org/details/marc_records_scriblio_net