I see no reason your book could not include and reference a different font set (see caveat)...
But if the letters are not rendering, then clearly it doesn't.
...
Caveat: They are actually a number or reasons your book -- or really, any book -- might not include different fonts. Scanned converted books rarely would as the automated software that does that sort of thing isn't smart enough to recognize the need or resourceful enough to obtain the font. Another issue, more applicable to epub original works, pertains to licensing. There may be costs and restrictions related to re-rendering a particular font in an electronic medium.