OpenURL lookup now works for books. this means that all that's necessary to add scrapable book metadata to a page is an ISBN, as shown below:
<span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:book&rft.isbn=1579550088"></span>
also, we can now scrape Open WorldCat and Wikipedia Book Sources pages with no specialized code involved.
i'm still looking for a better way of looking up journal article metadata. it's currently implemented with CrossRef, but CrossRef simply will not work without a DOI, and is also incomplete (only holds the last name of the first author).