ePUB renderers often have no support for any scripting capabilities, and the specification certainly does not mandate any script language, and actually disencourages them. Also, the subset of XHTML supported by ePUB (
http://www.idpf.org/doc_library/epub...htm#Section2.2) does not include the "Intrinsic Events" module, which contains "onclick" et al.
So yes, dynamic content is largely not supported by the ePUB spec (nor by ePUB readers). In the specification linked above you have a list of what
is (or should be) supported, both in XHTML and CSS.