If you do some searching on MobileRead, you will find some information on features such as small-caps. One I had saved from a few years back was:
Code:
font-variant: small-caps; /* high-level property */
font-variant-caps: small-caps; /* high-level property */
-moz-font-feature-settings: 'smcp'; /* low-level (old Firefox) */
-webkit-font-feature-settings: 'smcp'; /* low-level (old Webkit) */
font-feature-settings: 'smcp' on; /* low-level (all new browsers) */
which worked on a couple of ePub3 ebooks with an OTF font with small caps.
Edit: I never bothered to break the code down to see which option actually triggered small caps in the ebooks I was playing with.