Many of the options for different conversions are accomplished by command-line options, which are fed to xsltproc by what that program calls string parameters. Here are two examples:
xsltproc -stringparam html.knowl.example no mathbook-html.xsl fauna.xml

The first will make <example> content render on a page, rather than hidden in a knowl, which is the default for a conversion to HTML. And the second will use a larger overall font size, while trying to preserve the same number of characters per line (with consequent smaller margins).