In many disciplines in the arts,
humanities and social sciences, books are a very significant medium for
publication of new research. Databases which only count citations in the
journal literature are under-reporting the impact of publications in
these disciplines.
Web of Science added the Book Citation Index
in 2012. Content is comprised of scholarly books, both Series and
Non-series that present fully referenced articles of original research,
or reviews of the literature. It may yield some useful book-metrics for some disciplines.
It should be possible to check for
citations to a particular publication in any database which includes the
full text of books (in other words, any database of electronic books).
The largest such database is Google Books, but it is far from comprehensive.