  The last decade has seen two significant phenomena emerge in research
communication: the rise of open access (OA) publishing, and evidence of online
sharing in the form of altmetrics. There has been limited examination of the
effect of OA on online sharing for journal articles, and little for books. This
paper examines the altmetrics of a set of 32,222 books (of which 5% are OA) and
a set of 220,527 chapters (of which 7% are OA) indexed by the scholarly
database Dimensions in the Social Sciences and Humanities. Both OA books and
chapters have significantly higher use on social networks, higher coverage in
the mass media and blogs, and evidence of higher rates of social impact in
policy documents. OA chapters have higher rates of coverage on Wikipedia than
their non-OA equivalents, and are more likely to be shared on Mendeley. Even
within the Humanities and Social Sciences, disciplinary differences in
altmetric activity are evident. The effect is confirmed for chapters, although
sampling issues prevent the strong conclusion that OA facilitates extra
attention at whole book level, the apparent OA altmetrics advantage suggests
that the move towards OA is increasing social sharing and broader impact.
